AP Chemistry - ABSOLUTE COMPLETE MIDTERM!!!!!!
Acids vs Bases
Acids - Sour taste • Acetic acid in vinegar • Citric acid in citrus fruits (Ex. Lemon) Bases - Bitter taste • Poisonous plants (people reject this flavor) • Broccoli, Turnip, baking soda - Feels slippery - React with oils in ur skin to form soap - Many cleaning products contain NH3 - Blood - Drain Cleaner contains KOH
Molecular mass
(Molar of molecular compound) Is used to refer to molecules that can exist independently. It is the mass of one molecule
Avogadro's number
(N_A) 6.022 x 10^23 mol^-1
Van der Waals equation
(P+n^2a/V^2)(V-nb)=nRT = P = actual or measured P (atm) = n = moles of gas = a and b = constants for the specific gas in ? = V = actual or measured V (L) = T = temp. (K) = R = 0.0821 L•atm/mol•K
Bond Energy - The amount of energy that is...
...required to break the bond between 2 specific atoms in a molecule = ... released when a bond forms between the same 2 atoms
All 3 of the following conditions must be met in order for a reaction to occur
1) There must be a collision 2) The collision must occur with an orientation that could cause a reaction 3) E(collision) >_ E(a) • In most cases, only a small percentage of collisions result in reactions
Alloy
A solid solution composed of two or more metals or one or more metals and one or more non-metals Ex. Steel
Beer-Lambert Law
A=Ebc A = absorbance E = molar absorptivity (M^-1 cm^-1) b= path length of sample (cm) c = concentration (M) • E describes how intensely a sample of ions or molecules absorbs light at a specific wavelength • In most experiments, path length and wavelength remain constant, so E also remain constant, and absorbance, A, is only proportional to concentration, c
Label acid, base, conjugate acid, and conjugate base h) 2NH3 <—> NH4+ + NH2-
A&B CA CB
Label acid, base, conjugate acid, and conjugate base g) 2H2O <—> OH- + H3O+
A&B CB CA
1st Ionization Energy
A(g) --> A+(g) + e- The minimum amount of energy that is required to remove an outermost, least tightly held, electron from an atom in the gas phase
Electrons do not follow ________. A _________ describes an electron's possible positions in three-dimensional space, and is often called an _________
Orbits, Wave function; orbits
How can u tell what gets oxidized and what gets reduced??
Oxidation numbers = Positive or negative number that indicates how many electrons an atom has gained, lost, or shared to become stable
Ionization Energy: 2nd ionization potential for an atom is always greater than the 1st.
Radius reduced after 1st e- is removed, and ration of protons to e-s increases
The electrons that are furthest from the nucleus are partly "_________" by the inner core electrons. This shielding effect (__________ from the inner core electrons) reduces _____________between the outer electrons and the nucleus.
Shielded; electrostatic repulsion; electrostatic attractions
What is the difference between a sigma and pi bond?
Sigma- result from the overlap of orbitals Pi- result from the side to side interaction between unmorphed p-orbitals - Pi bonds r only present in double and triple bonds, whereas sigma bonds r present in single, double, and triple bonds
Why do noble gases not have electronegativity?
Since the noble gases already have eight electrons in their outer shells, they don't want to attract any more. Since electronegativity measures the amount of attraction between an atom and an electron, noble gases do not have electronegativity.
Electronegativity: An elements ability to ________ e-s in a chemical bond. E-s will spend ______ time around the more electronegative element in a chemical bond
attract; more
In all shells, electron density near the nucleus ___________ with each subsequent subshell that is added. Thus, the shielding effect __________ for each subshell that is added.
decreases; increases
= As the number of bonds between two atoms increases, the bond length ______, the bond energy _______, and the PE ________. = As the electron density between the positive nuclei increases, the attractive forces between the protons and the bonding electrons _________. = Do single or triple bonds have the hardest melting/boiling point??
decreases; increases; decreases; increases; Triple
If given an ionic compound and told it sits for an extended period of time...
it is a disproportionation reaction and the metallic ion should be in an intermediate oxidation state. This metal will get both oxidized and reduced. Oxidize to highest ox state — if u don't know what that is increase it by one, and reduce it to the pure metal
1st Order Integrated Rate Law
ln[A]t = -kt + ln[A]0 • A plot of ln[A]t vs t produces a straight line for 1st order reactions • Used to determine if a reaction is 1st order, as a straight line will only occur if the reaction is 1st order Slope = -k
Taking the natural log of both sides of the Arrhenius Equation gives...
ln k = -E(a)/R (1/T) + ln A • A graph of ln k versus 1/T produces a straight line • The activation energy, E(a), can be determined after calculating the slope of the line • Slope = -E(a)/R
smaller ion ______ condensed than larger ion and attract ____ more molecules to itself
more; more
If given a strong acid and a strong base...
net ionic always H+ + OH- —> H2O
Ratio of isotopes
of a certain element in any pure sample of a given compound is constant. If we could calculate the average mass of all the atoms of an element in a pure sample, we would obtain the average atomic mass of that element, which is given on the periodic table. As the ratio of the different atoms of each element that form a given compound is constant, the ratio of the masses of the constituent elements in a pure sample of that compound will also be constant
Percentage by mass
of an element in a pure sample of a compound or a component in a substance.
Atomic radius
one-half the distance between the nuclei of two atoms of the same element when the atoms are joined
Isoelectronic species
share the same electronic configurations, but have different radii
If given a weak acid and weak base...
show H+ transfer
If given a soluble ionic compound and water...
simply show the dissociation of the compound
Ionic Radius: Cations are __________ than neutral atoms. Anions are ___________ than neutral atoms.
smaller; larger
Solvent vs solute
solvent = Substance that is more plentiful in a solution Solute = Substance that is less plentiful in a solution
Hybrid orbitals: Hybridization and Ideal Bond Angle with charge clouds (2-6) around the central atom
sp (180 degrees), sp^2 (120 degrees), sp^3 (109.5 degrees), sp^3d (120 and 90 degrees), sp^3d^2 (90 degrees)
Aufbau Principle
states that each electron occupies the lowest energy orbital available
Aufbau
states that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels.
Unit Cells
the smallest group of particles within a crystal that retains the geometric shape of the crystal
quantum mechanical model
uses complex shapes of orbitals (sometimes called electron clouds), volumes of space in which there is likely to be an electron.
Which isotope is more likely to bond with oxygen, C-12 or C-14? Explain.
Both isotopes are equally likely to bond with oxygen. Having more or less neutrons in an isotope doesn't change its chemical reactivity
Is CO2 an empirical formula, a molecular formula, or both? Explain.
Both! There is exactly 1 C atom and 2 O atoms in each CO2 molecule, so CO2 is the molecular formula. 1 C : 2 O is also the smallest whole number ratio of C atoms to O atoms, making it an empirical formula as well.
Explain why Cl2 is a gas and Br2 is a liquid at 25'C and 1 atm
Br2, both non-polar and only LDF but Br2 is larger and has more e-s, making it more polarizable than Cl2 • Br2 experiences greater LDF • Bc of stronger FoA, Br2 exists as a liquid at 25'C and 1 atm, while Cl2 exists as a gas
Diatomic molecules
BrINClHOF = 2 diatomic molecules that contain atoms from the same groups in the same proportions: — Will have the same shape, and — will both be either polar or non-polar = This can help chemists design new materials: — Replacing an element from one group with another from the same group could lead to a new substance with similar properties — Ex. SiO2 can be used to make ceramics. SnO2 might work just as well — or better
F2 or Cl2 - Which structure had the longest bond length? Justify
Cl2 has the longest bond lengths. Cl has a larger atomic radius which means that the nuclei will be further apart
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces M. F2 or Cl2
Cl2, bc both LDF but Cl2 is larger and has more e-s, making it more polarizable than F2 • Cl2 experiences greater LDF • As a greater amount of energy is required to break stronger FoA, boiling pt of Cl2 is higher
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces f. Cl2 and H2
Cl2, bc both LDF but Cl2 is larger and has more e-s, making it more polarizable than H2 • Cl2 experiences greater LDF • As a greater amount of energy is required to break stronger FoA, boiling pt of Cl2 is higher
The force of attraction _____________ as the distance between the outermost electron and the protons ___________
Decreases; increases
Suppose u have 2 identical 1.0 L sealed containers. Both containers r kept at exactly 25'C. One vessel contains only Ne gas at 1.5 atm, and the other contains only Xe gas at 2.5 atm b. What variable must be changed in order to decrease the average KE of the Xe atoms??
Decreasing the T is the only method for decreasing the average KE of any system
Why is the 1st ionization energy for Li less than that of Ne?
For both atoms, the e- is removed from the n=2 shell. However, Ne has more protons in its nucleus. According to Coulomb's Law, the force of attraction between charged particles increases as the charge (in this case the number of protons) increases. As the force of attraction of the outermost e- in greater in Ne, it requires more energy to remove one of those e-
Not all collisions btwn reactants result in the formation of products for any elementary reaction. Explain why this is.
For most reactions, most collisions don't cause a chemical reaction • Orientation of each collision is completely random • Reactants must collide with an orientation that is conductive to the formation of a bond • Also, collisions must posses sufficient energy (activation energy) to produce a reaction
Magnesium ribbon is placed into a solution of copper (II) chloride. a. What is reduced in the reaction?
Mg + Cu2+ → Cu + Mg2+ Cu 2+
Mg^2+ and F- r isoelectronic - which ion has smaller radius? - Explain why radii of these 2 ions r different sizes. Justify.
Mg^2+ -Both species have same e- config., and same # of e-s. Mg^2+ has 12 protons, while F- only has 9 protons. -Bc Mg^2+ has more protons, its nucleus applies greater force of attraction on its e-s, thereby pulling them closer to nucleus. -According to Coulomb's Law, force of attraction acting on an e- increases as more protons r added to nucleus which gives Mg^2+ a smaller radius.
1st Ionization energy
Minimum amount of energy required to remove the least tightly held e- from an atom or ion in gas phase.
1st Ionization energy: ______________ amount of energy required to remove the least tightly held e- from an atom or ion in gas phase. Energy must always be ________ to remove an e-
Minimum; added
Benzene, a cyclic hydrocarbon, C6H6, is burned in air. a. Identify the substance oxidized and the substance reduced in the reaction.
2C6H6 + 15O2 → 12CO2 + 6H2O Carbon
Solid potassium metal is added to water. a. Write the balanced reduction half reaction.
2Na + 2H2O → 2Na+ + 2OH- + H2 2H2O → 2OH- + H2
Coulomb's Law
The relationship among electrical force, charges, and distance: The electrical force between two charges varies directly as the product of the charges and inversely as the square of the distance between them.
The mass of one 12-C atom is exactly _________. All other atoms are measured on a scale relative to 12-C.
12 amu
238 / 92 U isotope Protons? Neutrons? Electrons? Mass?
92 protons 146 neutrons 92 electrons 238 amu
Concentrated hydrobromic acid is poured into a solution of potassium permanganate. a. How many electrons are exchanged according to the reaction? b. Identify the oxidizing agent.
2(5e- + 8H+ + MnO4- → Mn2+ + 4H2O) 5(2Br- → Br2 + 2e-) 10e- + 16H+ + 2MnO4- → 2Mn2+ + 8H2O 10Br- → 5Br2 + 10e- 16H+ + 2MnO4- + 10Br- → 2Mn2+ + 8H2O + 5Br2 10e- MnO4- or KMnO4
What charge do Group 2A elements acquire as ions?
2+
1. Short saturated fatty acid 2. Long saturated fatty acid highest viscosity at 25'C??
2, bc both non-polar and LDF but 2 is larger and contains more e-s, which makes it more polarizable • intermolecular FoA btwn the molecules in a pure sample of 2 would be stronger • 2 would higher viscosity, became of stronger LDF
What charge do Group 6A elements acquire as ions?
2- for non-metals and 2+ or 4+ for metals
Label acid, base, conjugate acid, and conjugate base j) HI + H2O —> I- + H3O+
A B CB CA
Solution
(Homogenous mixture) • homogenous mixture of 2< substances • Macroscopic properties don't vary within the sample • Components cannot be separated by filtration • Components can be separated by methods that alter intermolecular forces - distillation and chromatography • No components r large enough to scatter visible light
London Dispersion Forces (LDF)
(Induced Dipole - Induced Dipole) = These forces exist btwn all species: atoms, ions, non-polar molecules and polar molecules - They contribute to the overall FoA btwn all particles = LDF r only intermolecular force that keep assemblages of non-polar species together = Caused by Coloumbic interactions btwn temporarily induced dipoles of neighboring species that result from their e- distributions = Instantaneous charge distributions r polar = Averaged over time this atom is non-polar
The Law of Definite Proportions
(Joseph Proust) Different pure samples of the same compound always contain the same proportions of each element by mass. e.g. Water is always 88.8% oxygen and 11.2% hydrogen by mass. Water is always found in these proportions by mass.
Suspension
(Mechanical mixture) • Heterogeneous mixture of 2< substances • Macroscopic properties r different at different locations within the sample - sizes, shapes, and concentrations of particles can vary • In some cases, components can be separated through filtration
Formula mass
(Molar Mass) Usually refers to the basic unit in a network solid. It is the mass of one of these basic units
Physical Processes
(Phase Change) - Involve changes in intermolecular interactions - Properties change but the composition remains the same - Ex. = phase changes and formation or separation of mixtures - Ex = NO(s) —> NO (L) NH3 (L) —> NH3 (aq)
Covalent Network Solids (SiO2) (Si and SiC)
(Quartz) (SiC - empirical formula for Quartz) = covalent network of SiO4 tetrahedra = every Si atom is covalently bonded to 4 O atoms = Every O atom is covalently bonded to 2 Si atoms (Si and SiC) (Si - Forms a covalent network with itself) = A 3-D network with a geometry that is similar of that of a diamond
Oxidation Reduction Reactions
(Redox Reactions) = e- transfer reactions - oxidized • loses e-s - reduced • gains e-s
mass number
(a) equal to the number of protons plus the number of neutrons (a/z C)
intramolecular forces
(bonds) forces within molecules. Forces caused by the attraction and repulsion of charged particles
Activity series order of increasing oxidation and which order to write elements in
(least) Au, Pt, Ag, Cu, Fe, Zn, Mg, Ca, Ba, K (most) • Elements will oxidize anything below it in this series • easier (s bottom) + harder (aq top) —> harder (s top) + easier (aq bottom)
Steel - an ______ alloy
(interstitial) • Carbon fills some spaces btwn Fe atoms • Pure Fe lacks directional bonds • Steel is more rigid, less malleable, and less ductile than pure iron, as a result of the strong directional bonds that form btwn C and Fe atoms • Density of steel is greater than that of pure Fe, as interstitial atoms don't expand the lattice by much
If given an acid and a nonmetal...
(remember nonmetals want to be reduced) the nonmetal will gain e-s from the anion of the acid. The hydrogen ion of the acid is a spectator
If given a metal and water...
(remember that metals want to be oxidized) oxidize the metal and reduce the water. Write the water as HOH and recall this works just like any other single replacement
If given an acid (except nitric) and a metal...
(remember the metals want to be oxidized) the metal will lose e-s to the hydrogen forming H2 and the metal ion. The anion of the acid is a spectator
Brass - a __________ alloy
(substitutional) • Zn atoms r substituted for some Cu atoms • Alloys remain malleable and ductile • Density normally lies btwn those of the component metals
Atomic number
(z) the number of protons (or electrons) in a neutral atom
What possible charge(s) can iron acquire as an ion?
+2 and +3
What possible charge(s) can lead acquire as an ion?
+2 and +4
The space filling models for 2 diatomic molecules r shown below 1. Smaller radius 2. Larger radius b. Which structure has the greatest bond energy between the central and a terminal atom? Justify
- 1 bc 1 has a smaller radii which means that nuclei will be closer together - According to Coulomb's Law, forces of attraction between nucleus of one atom and the Ve- of another increases as distance decreases - Also, PE decreases as Ve- from one atom approach the nucleus of another - To separate the atoms and break the bond, the same amount of energy that evolved must be added - Thus, it would require more energy to break a bond in 1 than it would to break a bond in 2
The space filling models for 2 diatomic molecules r shown below 1. Smaller radius 2. Larger radius c. Which structure has the least PE associated with its bonds? Justify
- 1 bc PE decreases as Ve- from 1 atom approaches the nucleus of another - Since the bonds in 1 r shorter, they contain less PE
Non-Bonding Orbital
- A MO that is at the same energy level as the one atomic orbital that it was derived from - E-s that occupy these orbitals don't cause stability or instability - Orbitals that contain lone pairs
Anti-Bonding Orbital
- A MO that is higher in energy than any atomic orbitals from which it was derived - E-s that occupy these orbitals cause instability
Bonding Orbital
- A MO that is lower in energy than any atomic orbitals from which it was derived - E-s that occupy these orbitals cause stability
Pure sample of iron and a sample of steel - What type of alloy is steel?
- A interstitial alloy
Limitations of the Lewis Structure Model Part 3) Incomplete Octets and other issues
- Accepted Lewis structure may have a center element without a full octet but the formal charges work out - Try to double bond: 2 non-zero formal charges and negative formal charge should be on most electronegative element - However, we don't have evidence that supports this structure (Double bond structure) — Experiments have shown that single bond length is less than it should be — suggests resonance and bond order greater than 1 - Electronegative difference suggests that bonds have a fairly high ionic character - None of these structures r 100% correct — Suggested that actual structure is a resonance of all 3, and incomplete octet is dominant form
Brônsted - Lowery Acids and Bases
- Acids donate protons • H+ ions fall off of the acid - Bases accept protons • Pick up H+ ions
Charge clouds of both methane (CH4) and ammonia (NH3) r arranged in a tetrahedral geometry. Explain why the actual bonds angles in methane r 109.5 degrees and actual bond angles in ammonia r 107.3 degrees
- All 4 charge clouds around C atoms in CH4 r bonds, so they r same distance apart and repel one another with the same force - NH3 has 3 bonds and 1 lone pair and 2 lone e-s spend most of their time closer to N atom than the bonding pairs - This also puts the lone pair in a position that is closer to the bonding pairs so lone pair exerts a slightly greater repulsive force on the bonding pairs, which causes them to move a little closer together
Although we draw all possible locations of a double bond for resonance structures, we know that the idea of the double resonating between the locations is ultimately incorrect. we know this bc...
- Bond length of all bonds is the same and lies in between the length of a single bond and length of a double bond
Metallic Solids
- Bonding is not covalent — not enough e- to fill octets - Bonding results from the attractions between nuclei and delocalized Ve- moving throughout the structure - Bond strength increases as the number of bonding e- increases
Identify which ionic solid will have the higher melting temperature. Justify a. NaCl or KBr
- Both ionic solids, so they have very high melting temperatures due to strong forces of attraction between ions - According to Coulomb's Law, forces of attraction (lattice energy) increase as distance between ionic centers decrease and as charges on ions increase - 2 sets of ions carry the same charges; however, Na+ has a smaller ionic radius than K+, and Cl- had a smaller ionic radius than Br-. - Thus, distance between ionic centers of Na+ and Cl- is less than distance between ionic centers of K+ and Br- - This means that NaCl must absorb more energy to overcome these forces of attraction, and thus, it has a higher melting temperature
Identify which ionic solid will have the higher melting temperature. Justify e. MgO or Al2O3
- Both ionic solids, so they have very high melting temperatures due to strong forces of attraction between ions - According to Coulomb's Law, forces of attraction (lattice energy) increase as distance between ionic centers decrease and as charges on ions increase - An increase in ionic charge is; however, the most significant factor in determining the strength of the bonds between atoms - As the ions in Al2O3 carry charges of 3+ and 2-, while the ions in MgO carry charges of 2+ and 2-; forces of attraction between the ions in Al2O3 r greater - This means that Al2O3 must absorb more energy to overcome these forces of attraction, and thus, it has a higher melting temperature
Identify which ionic solid will have the higher melting temperature. Justify c. BeF2 or LiF
- Both ionic solids, so they have very high melting temperatures due to strong forces of attraction between ions - According to Coulomb's Law, forces of attraction (lattice energy) increase as distance between ionic centers decrease and as charges on ions increase - An increase in ionic charge is; however, the most significant factor in determining the strength of the bonds between atoms - As the ions in BeF2 carry charges of 2+ and 1-, while the ions in LiF carry charges of 1+ and 1-; forces of attraction between the ions in BeF2 r greater - This means that BeF2 must absorb more energy to overcome these forces of attraction, and thus, it has a higher melting temperature
Identify which ionic solid will have the higher melting temperature. Justify d. CaO or CaCl2
- Both ionic solids, so they have very high melting temperatures due to strong forces of attraction between ions - According to Coulomb's Law, forces of attraction (lattice energy) increase as distance between ionic centers decrease and as charges on ions increase - An increase in ionic charge is; however, the most significant factor in determining the strength of the bonds between atoms - As the ions in CaO carry charges of 2+ and 2-, while the ions in CaCl2 carry charges of 2+ and 1-; forces of attraction between the ions in CaO r greater - This means that CaO must absorb more energy to overcome these forces of attraction, and thus, it has a higher melting temperature
Identify which ionic solid will have the higher melting temperature. Justify b. NaCl or MgS
- Both ionic solids, so they have very high melting temperatures due to strong forces of attraction between ions - According to Coulomb's Law, forces of attraction (lattice energy) increase as distance between ionic centers decrease and as charges on ions increase - An increase in ionic charge is; however, the most significant factor in determining the strength of the bonds between atoms - As the ions in MgS carry charges of 2+ and 2-, while the ions in NaCl carry charges of 1+ and 1-; forces of attraction between the ions in MgS r greater - This means that MgS must absorb more energy to overcome these forces of attraction, and thus, it has a higher melting temperature
CCl4 is non-polar, but CH2Cl2 is polar? Explain why this this is by discussing shape, polarity of bonds, and whether or not dipoles cancel
- Both r tetrahedral and all bonds r polar - CCl4 cancel, making structure non-polar but dipoles in CH2Cl2 don't cancel - Cl is more electronegative than H, so 2 H atoms acquire partial + charges - Polar overall compound as it acquires + and - end
Properties of Ionic solids -Cleave along planes:
- Brittle 3D structure - Ions line up in a repetitive pattern that maximizes attractive forces and minimizes repulsive forces - Not malleable or ductile (able to be hammered or pressed permanently out of shape without breaking or cracking)
C2H2 or C2H6 H-C=_C-H or 2 C surrounded by 6 H w/ single bonds e. C-C bond contains the greatest amount of PE in which structure?? Justify
- C2H6 bc OE of Ve- decreases as they approach the nucleus of another atom - Since the C-C bond length in C2H6 is longer, it has more PE
Extended Pi Bonding Ex. Benzene C6H6
- CH is every corner - Alternating single and double bonds that can flip-flop - Each p-orbital can overlap with 2 different p-orbitals - Leads to delocalization of e-s - Can be used to explain resonance in Lewis structures
In which structure, CO3 2- or CO2 , is the bond energy between the C atom and each O atom the greatest? Explain
- CO2 bc it has 2 bonds between each C and O whereas CO3 2- has only 1.33 bonds between each C and O - Bc there is a greater force of attraction between bonding atoms in CO2, it requires more energy to break the atoms apart in this structure
In which structure, CO3 2- or CO2 , is the bond length between the C atom and each O atom the shortest? Explain
- CO2 bc it has 2 bonds between each C and O whereas CO3 2- has only 1.33 bonds between each C and O - Greater number of bonds between atoms means the e- density between the nuclei of the atoms is greater - As the e- density increases, the attractive forces between protons of the bonding atoms and the e- involved in bond increase - Bond length decreases as the force of attraction increases
In which structure, CO3 2- or CO2 , has the most PE associated with its individual bonds? Explain
- CO3 2- bc PE decreases as Ve- from one atom approaches nucleus of another - Since bond lengths in CO3 2- r longer, they contain more PE
Pure sample of iron and a sample of steel - Explain how carbon changes the properties such as more rigid, less malleable, less ductile, and density of steel is also greater than the density of pure iron
- Carbon atoms from strong directional bonds with neighboring iron atoms, and pure iron lacks directional bonds - This is why steel is much more rigid, less malleable, and less ductile than pure iron - Density of steel is also greater than the density of pure iron bc interstitial carbon atoms do not increase overall volume or expand the lattice of iron by very much
VSEPR Theory Step 1. Count # of charge clouds, bonds, and lone pairs around the central atom
- Each item in this list is a single charge bond — Single bond = has 2 e-s — Double bond = has 4 e-s — Triple bond = has 6 e-s — Lone pair = had 2 e-s — Single unpaired e- = 1 lone e- - Each item on this list is considered 1 bond: — single bond = has 2 e-s — double bond = has 4 e-s — triple bond = had 6 e-s - Each item on list is considered a lone pair: — Lone pair = has 2 e-s — Single unpaired e- = had 1 e-
Explain why CH4 has a tetrahedral geometry, while SF4 has a seesaw shape
- Central atom in methane is surrounded by 4 charge clouds - All of these charge clouds r bonding pairs and 4 bonding pairs repel one another with the same force, causing them to move as far away from one another as possible and results in a tetrahedral with bond angles of 109.5 degrees - central atom in SF4 is surrounded by 5 charge clouds. 4 of these charge clouds r bonding pairs and 1 is a lone pair. A seesaw shale results from this configuration
Polyatomic Ions Defined - Polyatomic Ions:
- Combination of non-metals or metals and non-metals bonded together to form a polyatomic ion - Bonds between atoms r non-polar covalent or polar covalent
Grey Area (Both Chemical and Physical Process)
- Dissolving a salt in water involves breaking ionic bonds and creating ion-dipole interactions - Ex. = NaCl(s) —> Na+(aq) + Cl-(aq)
C=C=C - How is the double bond between the 1st and 2nd C formed?? Reference types of orbitals involved in bonds and the methods of bonding
- Double bond contains a sigma and double bond - Sigma bonds results from overlap of the sp^2 hybrid orbital on 1st C and the sp hybrid orbital on the 2nd C - Pi bond results from side to side interaction between unmorphed p-orbital on 1st C and one of the unmorphed p-orbitals on the 2nd C
Pi or sigma bonds - Extended networks of sigma bonds can cause a delocalization of e-s. Explain
- E-s shared in each pi bond - If a pi bond flip-flop back and forth between adjacent p-orbitals on 2 sides of an atom, the shared e-s in p-orbitals can be considered delocalized
F2 or Cl2 - Which structure has the least PE associated with its bond? Justify
- F2 bc PE decreases Ve- from one atom approaches nucleus of another - Since bond length in F2, is shorter, it contains less PE
F2 or Cl2 - Which bond has the greatest bond energy? Justify
- F2 bc it has a smaller radius which means that the nuclei will be closer together - According to Coulomb's Law, forces of attraction between nucleus of one atom and the Ve- of another increases as distance decreases - Also, PE decreases as Ve- from one atom approach the nucleus of another - To separate the atoms and break the bond, the same amount of energy that evolved must be added - Thus, it would require more energy to break a bond in F2 than it would to break a bond in Cl2
Resonance Structures
- For many molecules, double or triple bonds r located between different atoms - This can result in two or more possible Lewis structures that r equally valid — If u r asked to draw a Lewis structure for a molecule of polyatomic ion that exhibits resonance, must draw all possible structures with 2 way arrows
Polar Bonds
- Greater electronegativity differences lead to greater partial charges and greater bond dipoles
Types of solutions - Gas - Solid Solutions
- H2 gas can occupy the spaces btwn some metal atoms such ad iron, and palladium
Polar and non-polar molecules
- If a molecule is polar, it must have a dipole moment. μ μ = Q x r Q = absolute value of the net partial charge at each end of a molecule r = distance between positive and negative poles of a molecule
Extended Pi Bonding
- In organic chemistry terms, it is used to describe the situation that occurs when π systems (e.g. double bonds) are "linked together" - exists over a longer series of atoms (e.g. C=C-C=C or C=C-C=O. etc.). - results in a extension of the chemical reactitvity.
Strength of Ionic Bonds
- Ionic bonds r very strong so it requires a lot of energy to melt or vaporize these solids — Very endothermic
Crystalline Solids
- Ionic compounds do not exist as individual units containing one cation and one anion — NaCl doesn't exist as 1 Na cation bonded to 1 Cl anion - Ions r arranged in an orderly fashion that follows a pattern of repetition in 3D — Segments that repeat in 3D r called unit cells - Macroscopic structures usually have flat surfaces that make definite angles to one another — Due to that they cleave along planes
Arrangement of Ions
- Ions in an ionic solid r arranged in order to maximize Coulombic forces of attraction between cations and anions and to minimize repulsive forces between ions with like charges - Way in which ions r arranged depends on — Relative size of cations and anions — Ratio of cations to anions
Limitations of the Lewis Structure Model Part 1) Resonance
- Many of the double bonds r shown in accepted Lewis structures r not really double bonds - They r 1.5, 1.33, or 1.25 bonds - In some cases, resonance must be used to refine a Lewis structure in order to obtain qualitatively accurate predictions about the effective # of bonds, bond energy, and bond length
Spectroscopy
- Method of analysis which is based upon the absorbance of electromagnetic radiation by matter - Used 2 acquire data pertaining to the concentration of colored species I(o) = I(T) + I(A) I(o) = intensity of electromagnetic radiation striking sample I(T) = intensity of electromagnetic radiation exiting sample I(A) = intensity of electromagnetic radiation absorbed by the sample
Limitations of the Lewis Structure Model Part 4) Expanded octets also fail octet rule
- More than 8 Ve- in octet
Properties of Covalent Compounds
- Most covalent compounds have much lower melting and boiling points than ionic compounds - Covalent solids r usually soft and flexible - Most covalent compounds do not conduct electricity when dissolved in water. Acids r an exception to this rule
Properties of Ionic solids -Solubility and Conductivity
- Most r soluble in polar solvents - They conduct electricity only when molten or dissolved in a polar solvent as the charged particles r free to move — The higher the concentration of ions in a solution, the higher the electrical conductivity - Smaller ion is, more condensed magnetic field and more attractive it is to water — smaller = stronger ability to attract water
Are ionic solids malleable?
- No, bc ions r lined up in a repetitive 3D pattern. - When an ionic solid is hit with a hammer, one plane will slide along an adjacent plane. - When this happens, ions with like charges move closer to one another, which will result in forces of repulsion between the planes. - These repulsive forces can cause solid to cleave along that plane. - For this reason, ionic solids r considered to be brittle, and not malleable
Metallic Bonding - Electron Sea Model
- Nuclei and inner core e- r localized which Ve- r free to move throughout the solid — Conduct Electricity — Conduct Heat — Malleable and Ductile —— Lack directional bonds
Bond energy / Bond length
- PE decreases as attractions between nuclei and Ve- pull the atoms closer together - Moving further to the left, bond (spring) is compressed and the PE rises - As atomic radii of bonding atoms increase, the bond length increases and the bond energy decreases — Closer proximity to the shared e- allows for a stronger force of attraction between protons and bonding e-s — When force of attraction is greater, it requires more energy to break the bond
polar covalent bonds
- Partial charges r = in magnitude and opposite in sign - atom w/ higher electronegativity develops partial - charge, as shared Ve- spends more time around it - atom w/ lower electronegativity develops partial + charge, which is = in magnitude to partial - charge of more electronegative atom - Partial charges increase as electronegativity difference increase - Sum of partial charges in any molecule or ion is always = to overall charge on species
The macroscopic properties of a pure sample of an unknown solid were examined in order to determine the type of bonding between particles. When hit with a hammer, it dents. When cleaned with steel wool it becomes very shiny. The solid conducts electricity but doesn't dissolve in H2O. Make a prediction about the type of bonding in this compound, Justify
- Properties of this solid indicate that it is a metal and the atoms r held together by metallic bonds - Metallic bonds r not directional, so they tend to be malleable - Malleable materials will dent when they r hit with a hammer - The outer surfaces of metals will oxidize in the presence of oxygen gas - If oxidized surface is cleaned off, metals r shiny - Metals conduct electricity in solid state
The macroscopic properties of a pure sample of an unknown solid were examined in order to determine the type of bonding between particles. The solid is soft and can be cut with a knife. It starts melting at 35 degrees Celsius. It doesn't dissolve in H2O - instead it floats on the surface. Make a prediction about the type of bonding in this compound. Justify
- Properties of this solid indicate that it is composed of molecules - Individual molecules r held together with covalent bonds - Molecular solids tend to be relatively soft, have low melting points and low boiling points - Some molecular solids dissolve in H2O and some don't
The macroscopic properties of a pure sample of an unknown solid were examined in order to determine the type of bonding between particles. The solid is very hard. When it is broken, the fragments form similar 3D shapes. When dissolved in water the resulting solution conducts electricity. Make a prediction about the type of bonding in this compound. Justify
- Properties of this solid indicate that it is held together by ionic bonds - Unit cells in ionic solids repeat in a regular 3D patterns and these solids tend to cleave along planes, which would give the fragments similar 3D shapes - Angles that the planes cleave along will be the same - When dissolved in H2O, ionic compounds dissociate into individual ions which r charged particles that r free to move - For this reason, ionic compounds r able to conduct electricity when dissolved in polar solvents
Properties of Steel
- Pure iron lacks directional bonds - Steel is more rigid, less malleable, and less ductile than pure iron, as a result of the strong directional bonds that form between carbon and iron atoms - The density of steel is greater than that of pure iron, as interstitial atoms do not expand the lattice by much (D = M/V)
Pure sample of iron and a sample of steel - In what way have some of the bonds changed when this alloy was formed?
- Pure iron only has metallic bonds, which lack direction - In steel carbon forms strong directional bonds with the neighboring iron atoms
Bond Polarity
- Shared e-s spend more time around the most electronegative element in the chemical bond - This gives the more electronegative element a slightly negative charge and the less electronegative element a slightly positive charge
Molecular Models - Space-filling model
- Shows difference in the atomic radii of the bonded atoms - Shows relative bond length - Doesn't show the 3D positions of atoms very well - Doesn't show the number of bonds between atoms
Molecular Models - Ball-and-Stick Model
- Shows the 3D positions of atoms well - Shows single, double, and triple bonds - Balls r not proportional to the size of the atoms - Sticks r not proportional to and greatly exaggerate the bond length
Strengths of Bases
- Stronger base always accepts the most protons in an acid/base reaction - There r always 2 bases 1. Base on the reactants side of the equation, and... 2. Conjugate base on the products side on the equation
Dipole-Dipole
- The attractive forces between the negative end of one polar molecule and the positive end of another polar molecule - Molecules with dipole moments experience Coulombic interactions when they r in close proximity to one another. - FoA increase as magnitude of dipoles increases
Electronegativity Difference
- The difference between these classification is not distinct — it is a continuum. - All polar covalent bonds have some ionic character and ionic bonds can have some covalent character
Bond energy/bond length graph
- The higher the bond energy, the 'stronger' we say the bond is between the two atoms, and the distance between them (bond length) is smaller. For instance, the HO-H bond in a water molecule requires 493 kJ/mol to break and generate the hydroxide ion (OH-). - At 0.074 nm, bond length of H2, energy is at its lowest point. This is how H2 exists - on average. Bonds can be thought of as springs, so 0.074 nm is the midpoint of the oscillation
Bond Energy
- The potential energy of Ve- decreases as they approach the nucleus of another atom - Energy is released during the formation of a bond — Potential energy decreases as the atoms move close together - The same amount of energy must be added in order to break that specific bond — Potential energy increases as the atoms move away from one another
Substitutional Alloys
- The radius of the solute and solvent atoms r similar Brass - A substitutional alloy — zinc atoms r substituted for some copper atoms — Alloys remain malleable and ductile - The density normally lies between those of the component metals
Possible arrangements of Ions - Body Center Cubic
- This unit cell contains 8 corners x 1/8 of an ion + 1 central atom = 2 ion/unit cell
Possible arrangements of Ions - Space center cubic
- This unit cell contains 8 corners x 1/8 of an ion + 6 faces x 1/2 of an ion = 4 ion/unit cell
Possible arrangements of Ions - Simple Cubic
- This unit cell contains 8 corners x 1/8 of an ion = 1 ion/unit cell
Hydrogen Bonds
- Type of Dipole-dipole - Occurs btwn H that is covalently bonded to F, O, or N and another F, O, or N with at least one lone pair - 5-10 x stronger than other d^2 attractions
Pure sample of iron and a sample of steel - Identify 4 properties that change when Carbon is added to pure iron in order to make steel?
- When carbon is added to pure iron, the metal becomes more rigid, less malleable, and less ductile - Density of steel is also greater than the density of pure iron
Limitations of the Lewis Structure Model Part 2) The Octet rule fails when there r odd #s of Ve-
- When sum of Ve- of all atoms in a molecule is not an even #, the octet rule fails
Electronegativity
- an elements ability to attract bonding electrons toward itself in a chemical bond. - Increases as atomic radius decreases. - When 2 atoms are involved in a chemical bond, bonding electrons experience a greater attraction for the positive nucleus that is closest to them in accordance with Coulomb's law
Precipitation Reactions
- attractive forces btwn oppositely charged ions is greater than FoA btwn H2O molecules and the ions
Explain the electron sea model of metallic bonding. Explain the factors that make metals good conductors of heat and electricity
- e- sea model accounts for properties of metals. - Free movement of Ve- allows metals to conduct electricity. - e- movement also enables metals to conduct heat rapidly - If u heat 1 end of metal bar, u will transfer heat to the e-s in that area - These energized e-s will move to the other end of the bar, carrying heat with them
Formal Charge
- in some cases, atoms in a molecule can be assembled in different ways when drawing a Lewis diagram - Formal charge r calculated to identify the most stable or likely structure - Sum of the formal charges on each atom will be zero for a neutral molecule - sum of the formula charges on each atom will be = to the overall charge of the structure for a polyatomic ion
Chemical Processes
- involve the breaking and/or formation of chemical bonds - Substances r transformed into new substances that may have different properties - Temperature changes, production of light, formation of a gas, formation of a precipitate, and/or changes in color r indications that a chemical changes has occurred - Ex. = 2Na(s) + Cl2(g) —> 2NaCl(s)
Sigma or Pi Bonds - Which type of bond has a greater amount of bond energy? Justify
- sigma bc they result from the direct overlap of orbitals, and pi bonds result from the side to side interaction between unmorphed p orbitals. - Bc of this, sigma binds have a shorter bond length, so greater amount of bond energy
Reaction Mechanisms
- the series of steps that sum to the overall reaction • most reactions do NOT happen in 1 step
To know if a molecule is polar...
- u must know if the bonds r polar - u must know the overall shape
Explain each of the following occurrences by referencing the structure of the atoms in question (energy levels, orbitals, protons, etc.). -The first ionization energy of Mg is 738.1 kJ/mol, while the first ionization energy of Al is only 577.9 kJ/mol.
-(exception to the rule) Normally ionization energy increases as move from left to right across period in periodic table, bc shielding effect is similar and effective nuclear charge increases. -Reason for exception has to do w/ the e- config. of these elements. Mg has e- config. of 1s^2 2s^2 2p^6 3s^2, and Al has e- config. of 1s^2 2s^2 2p^6 3s^2 3p^1. -Requires less energy to pull only e- from p-orbital in Al, which is higher energy subshell, than it does to pull e- from full s-orbital in Mg, which is lower energy subshell -Lone e- in p-orbital of Al is at much higher energy than those in full s-orbital of Mg and being "shielded" by other e-s in lower energy subshells.
Explain each of the following occurrences by referencing the structure of the atoms in question (energy levels, orbitals, protons, etc.). -2nd ionization energy of Na is 4560 kJ/mol, while 2nd ionization energy of Mg is only 1450 kJ/mol.
-2nd e- removed from Na is taken from n=2 shell, whereas 2nd e- removed from Mg is taken from n=3 shell. -distance between nucleus and n=2 shell e-s is much less than distance between nucleus and n=3 e-s. Reduced distance means attractive forces between protons and n=2 e-s is greater -According to Coulomb's Law, forces of attraction increase as distance between e-s and protons decreases. -Greater attractive force, more energy required to remove an e-
Interstitial Alloys
-Atoms with a small radius occupies the spaces between atoms with a larger radius Steel - An interstitial alloy — Carbon fills some spaces between iron atoms
Explain each of the following occurrences by referencing the structure of the atoms in question (energy levels, orbitals, protons, etc.). -1st ionization energy of Mg is greater than 1st ionization energy of Ca.
-Ca has larger atomic radius than Mg, due to fact that Ve- of Ca r in 4s orbital and those of Mg r in 3s orbital -As radius of Ca is larger, its Ve- r held w/ smaller force of attraction, and requires less energy to remove them. -According to Coulomb's Law, forces of attraction decrease as distance between e-s and protons increases
Why are some processes endothermic?
-Consider how much energy is required to break bonds to how much energy is released as new bonds are formed. -Energy is released as bonds are formed (even if it an overall endothermic process
Covalent or ionic??
-Electronegativity difference is not the only factor that determines if the bond is covalent or ionic - Generally, bonds between a metal and non-metal r ionic and bonds between 2 non-metal r covalent - Examining the properties of compound is the best way to characterize the bond type
Why do halogens have negative e- affinity value, while noble gases have positive e- affinity value?
-Highest energy subshell (p-orbital) is full all of these elements and added e- would be only e- in higher energy subshell. -Shielding effect from inner core e-s is no large that energy must be added for them to accept additional e-. -Adding energy is endothermic, which is + energy value -Halogens need 1 more e- to fill octets. Bc of this, they will accept e- to fill highest energy subshells (p-orbitals) -In doing so, they give off energy. Giving of energy is exothermic process, which has a - energy value.
Electron Affinity: Positive Values (Group 8A)
-Highest energy subshell (p-orbital) is full for all of these elements -Added e- would be only e- in higher energy -Shielding effect from inner core e-s is so large that energy must be added for them to accept additional e-
Electron Affinity: Positive Values (Group 2A)
-Highest energy subshell (s-orbital) is full for all of these elements -Added e- would be only e- in highest energy p-orbital -Shielding effect from inner core e-s is so large that energy must be added for them to accept additional e-
Why do the Group 1A elements have negative e- affinity values, while Group 2A elements have positive e- affinity values?
-Highest energy subshell (s-orbital) is full for all these elements and added e- would be only e- in higher energy p-orbital -Shielding effect from inner core e-s is so large that energy must be added in order for them to accept additional e-. -Adding energy is endothermic, which is + energy value. Group 1A elements need 1 more e- to fill s-orbital and bc of this, they will readily accept an e- and give off energy. -Giving energy is exothermic process, which has - energy value.
Explain each of the following occurrences by referencing the structure of the atoms in question (energy levels, orbitals, protons, etc.). -1st ionization energy of Na is less than 1st ionization energy of Cl.
-Na has larger atomic radius than Cl. -Ve- of both elements r in same shell (n=3), so shielding effect experienced by Ve- of both elements similar -However, Ve- in Cl experience greater effective nuclear charge, as it has more protons in nucleus. -According to Coulomb's Law, forces of attraction acting on e- increases as more protons r added to nucleus. -Bc force of attraction on Ve- in Na is less than that in Cl, it requires less energy to remove e- from Na.
Ionic Radius: (Down a Group from Top to Bottom)
-New shells added (Principal quantum # increases) w/ larger orbitals -Ve- have more energy, less stable, and r further from nucleus -Outer e-s experience greater shielding effect and decreased effective nuclear charge -According to Coulomb's Law, force of attraction decreases as distance between e-s and protons increases
Atomic radius (Down a Group from Top to Bottom)
-New shells added (principal quantum # increases) with larger orbitals -Ve- have more energy, r less stable, and r further from nucleus -Outer e-s experience greater shielding effect and a decreased effective nuclear charge -According to Coulomb's Law, force of attraction decreases as distance between e-s and protons increases
Electron Affinity: (Down a Group from Top to Bottom)
-New shells are added (principal quantum # increases) with larger orbitals -Outer e-s experience greatest shielding effect and decreased effective nuclear charge -According to Coulomb's Law, force of attraction decreases as distance between added e- and nucleus increases. -e- affinity values generally become less - (less energy released) bc force of attraction between nucleus and added e- is weaker
Is energy released or absorbed when neutral sodium atoms react with chlorine gas to form solid sodium chloride, NaCl?
-Released and the process of bond formation is exothermic -Energy is always released during bond formation.
Describe the modifications to the shell model that r required due to the experimental PES data that was provided in the lecture.
-Shell model stated that e- follow orbits and orbits were given a quantum # (n=1, n=2, n=3...). All e- follow given orbit shared same quantized energy level. -In other words, all e- in n=2 of given atom possesses same energy and all e-s in n=3 of given atom possesses same energy. -PES data indicated that shell model must be modified. Shows that there r 2 possible ionization energies in n=2, which indicated e-s can be found in 2 sublevels in n=2 at 2 separate energy levels. PES data also shows that there r 3 possible ionization energies in n=3, which indicated that e-s can be found in 3 sublevels in n=3 at 3 separate energy levels. -Furthermore, it is evident that n=1 has one level that can hold up to 2 e-s, and 1st sublevel in n=2 can hold 2 e-s and 2nd can hold 6 e-s.
Hund's Rule
-When you have more than one orbital in a subshell (includes p, d, and f subshells) a single spin up electron is added to each orbital before you start adding spin down electrons. -every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin.
Hybrid Orbitals
-atomic orbitals around the central atom in a molecule must hybridize in order for bonding to occur
Properties of Ionic solids -Strong bonds
-very strong Coulombic forces of attraction between cations and anions — High melting points — Very hard — Low volatility (doesn't vaporize easily)
Determining Rate Law Steps
1) Chemists determine the rate law through experimentation 2) They use the rate law to figure out what the elementary steps are • The rate law tells them what the slowest step is • Then they try to figure out what the fast steps are • Through experimental detection of reaction intermediates, evidence is built to support proposed mechanisms
VSEPR Theory (2 Steps)
1) Count # of charge clouds, bonds, and lone pairs around center atom 2) Predict the shape
Why are H-bonds so strong?
1) F-H, O-H, and N-H bonds r very polar 2) These atoms r very small, so partial charges caused by the differences in electronegativity r highly concentrated 3) LP(s) on F, O, or N increases the already partially - charge on these atoms, thereby creating a stronger attraction for the slightly + H
Limiting Reactant, X(A) and P(A)
1) Find mole fraction of all gases present after the reaction is complete 2) Find total pressure in vessel after reaction 3) Find partial pressure of H2 after reaction
6 Rules for Determining Oxidation Numbers
1) For an atom in its elemental form, its oxidation # is 0 (Mg, H2, O3) 2) For a monoatomic ion, its oxidation # is = to its charge (Mg2+ = +2; Cl- = -1) 3) Oxidation # for O in molecular compound is -2 (H2O) (Exception: Peroxides: ON = -1 (Ex. H2O2) 4) Hydrogen (+1 when bonded to a nonmetal (Ex. HCl)) (-1 when bonded to a metal (Ex. MgH2)) 5) For other covalent compounds that don't contain H or O, most electronegative element has an oxidation # = to its charge as an ion (BF3: F oxidation # = -1) (PCl5: Cl oxidation # = -1) 6) Sum of oxidation #s for all atoms in a compound must = overall charge of that compound (H2O)
Melting Point of Ionic Solids - Which compound from each set has the greatest melting point? Why? 1) LiF and LiI 2) MgCl2 and MgO 3) NaF and MgI2
1) LiF, easier to melting/boiling (F smaller than I) 2) MgO, O is smaller than Cl2 3) MgI2, I2 is smaller than F
How to tell which structure is more likely from formal charges??
1) More likely Lewis Structure will have formal charges that r closer to or = to zero 2) If there r negative formal charges, they should reside on the more electronegative elements in the structure
Problems with Arrhenius Acids and Bases
1) Only true for bases that contain OH- • There r bases that don't have OH-, but still make solutions basic 2) Only true for reactions that take place in aqueous solutions
Factors Affecting Reaction Rate
1) Rate of collisions btwn reactants 2) Percentage of collisions with an orientation that could produce a reaction 3) Percentage of collisions possessing sufficient energy (activation energy) to produce a reaction
Limitations of the Lewis Structure Model (4 parts)
1) Resonance 2) Octet rule fails when there r odd numbers of Ve- 3) Incomplete octets and other issues 4) Expanded octets also fail the octet rule
Spectroscopy - 2 methods used for spectroscopic analysis
1) Ultraviolet/Visual (UV/Vis) spectroscopy • Examines transitions in electronic energy levels - Is used to probe the electronic structure of certain compounds • Is used to determine concentration of solutions that contain certain compounds 2) Infrared (IR) Spectroscopy • Examine transitions in molecular vibrations - Is used to detect the presence of different types of bonds and to identify molecules
Balancing Redox Reactions in Acidic Solutions
1) Write 2 unbalanced half-reactions • Oxidation/Reduction half-reactions For each of the half reactions: 2) Balance all atoms except for O and H 3) Balance for O by adding H2O molecules 4) Balance for H by adding H+ ions 5) Balance the charge by adding e-s 6) Cross multiply to cancel e-s 7) Add half reactions and cancel things that r the same
Procedure for Balancing Chemical Equations
1) Write the chemical formulas for all reactants and products 2) Balance elements that don't exist independently first by adding coefficients 3) Balance elements that exist independently last 4) Check to make sure that both sides are balanced
Compounds with Multiple Central Atoms (4 steps)
1) look at each central atom on its own (Everything it is bonded to is considered to be a terminal atom 2) Count the charge clouds and bonds around it 3) Predict shape around it 4) Isolate next central atom and repeat steps 1-3
What charge do Group 1A elements acquire as ions?
1+
What charge do Group 7A elements acquire as ions?
1-
Lewis structures (steps)
1. Count total Ve- 2. Put least electronegative atom in center and connect terminal atoms to it with single bonds 3. Complete octets for all terminal atoms except H atoms 4. Add up e- used and subtract them from total Ve-. Attach leftover e-s to central atom as lone pairs 5. Make multiple bonds to complete the octet of central atom 6. DON'T FORGET BRACKETS AND CHARGE!
Intermolecular FoA order
1. Ion-Ion (Ionic - Intra) (strongest) 2. Ion-dipole 3. H-bonds (small molecules can have very strong intermolecular attractions whereas H-bonds r present) 4. Dipole-dipole 5. Ion-induced dipole 6. dipole-induced dipole 7. LDF (Often strongest FoA btwn large species) (weakest)
Study of Reaction Rates
1. Rate of disappearance of a reactant 2. Rate of appearance of a product 3. Rate at which the overall reaction proceeds
3 factors affecting solubility
1. Structure = "Like dissolves Like" (polar dissolves polar; non-polar dissolves non-polar) 2. temperature = Different rules for different types of solutions 3. pressure = applies to Gas-liquid solutions
2nd Order Integrated Rate Law
1/[A]t = kt + 1/[A]0 • A plot of 1/[A]t vs t will give a straight line for 2nd order reactions • This is used to determine if a reaction is 2nd order, as a straight line will only occur if the reaction is 2nd order slope = k
Which subshell contains the lowest energy electron(s) in Na?
1s subshell -aufbau principle, electrons enter orbitals of lowest energy first -e-s in that subshell r closest to nucleus and experience greatest force of attraction according to Coulomb's Law. -Bc of this, those e-s r most stable
1. Unsaturated fatty acid 2. Saturated Fatty acid Highest boiling pt??
2 bc LDF r greater and molecules r linear, so they stack up better (can approach each other more closely) • means that 2 can produce more induced temporary dipoles than 1
The space filling models for 2 diatomic molecules r shown below 1. Smaller radius 2. Larger radius a. Which structure has the longest bond lengths? Justify
2 bc atoms in 2 have larger radii which means that nuclei will be further apart
Nickle (I) nitrate is allowed to stand for an extended period of time. a. Write the balanced reduction half reaction for the above.
2Ni+ → Ni + Ni2+ e- + Ni+ → Ni
Sulphur is burned in air. a. Is the above reaction a redox reaction? Justify your claim in terms of electrons.
2S + 3O2 → 2SO3 (Could also go to SO2) Yes, it is redox. Each sulfur loses 6 electrons and each of the three oxygens gains two electrons. IF you wen to SO2, the S loses 4 and each of the two O's gains 2.
An electron in ___ spends more of its time further from the nucleus than one in ______, but the electron density near the nucleus is greater for 2s electrons due to the first maximum. 2p electrons experience a _________________ from the 1s electrons than do the 2s electrons
2s; 2p; greater shielding effect
Copper wire is placed into a solution of nitric acid. a. What is reduced in the reaction? b. Write the balanced reduction half reaction. c. What is the oxidation number of nitrogen before and after the reaction occurs?
3(Cu → Cu2+ + 2e-) 2(3e- + 4H+ + NO3- → NO + 2H2O) 3Cu → 3Cu2+ + 6e- 6e- + 8H+ + 2NO3- → 2NO + 4H2O 3Cu + 8H+ + 2NO3- → 3Cu2+ + 2NO + 4H2O NO3- 3e- + 4H+ + NO3- → NO + 2H2O Before +5, after +2
Rate Law
3) rate of overall reaction A + B —> C + D Rate = k[A]^m • [B]^n Rate = rate of disappearance of reactants (M/time) • k = rate constant, or proportionality constant, depends on the specific reaction and temperature m = reaction order in terms of A n = reaction order in terms of B
What charge do Group 3A elements acquire as ions?
3+ (Tl can be 3+ or 1+)
What charge do Group 5A elements acquire as ions?
3- for non-metals and 3+ or 5+ for metals
Solutions of lead (II) nitrate and lithium phosphate are mixed. a. Is the above reaction a redox reaction? Justify your claim in terms of electrons. b. What are the spectator ions in the reaction? c. What is the oxidation number of lead before and after the reaction occurs?
3Pb2+ + 2PO43- → Pb3(PO4)2 No, it is not redox. The oxidation numbers on all substances remains the same indicating that no electrons are exchanged. NO3- and Li+ +2 before and after
Which subshell contains the electron with the lowest ionization energy in Al?
3p. -According to Coulomb's Law, force of attraction between two charged particles decreases as the distance between them increases, as distance is the denominator of the equation. -e- in n=3 shell are furthest from nucleus. When force of attraction decreases, energy required to remove e- also decreases. -Average distance between nucleus and e- decreases as subshells within a shell are added. Leads us to believe that ionization energy for a 3s e- would be less than 3p e- in same element (Coulomb's Law), but that is not the case. -e- density close to nucleus decreases for each subsequent subshell that is added to shell. Decreases in e- density close to nucleus increases shielding effect from e- in n=1 and n=2. -Increase in shielding effect has greater impact on force of attraction than Coulomb's Law when looking at subshells within a shell.
Which subshell contains the highest energy electron(s) in Na?
3s subshell. -aufbau principle, electrons enter orbitals of lowest energy first -e- in that subshell furthest from nucleus and experiences smallest force of attraction according to Coulomb's Law. -Attraction further reduced due to shielding effect from e-s in n=1 and n=2. -Bc of this, that e- is least stable.
Calculating Formal Charge
= (# of Ve- assigned to neutral atom) - (# of e- assigned to atom in structure) (# of e- assigned to atom in structure) = [# of lone e- around atom + (# of bonding e-)/2]
Boiling Points
= A liquid boils when its vapor pressure = atmospheric pressure - Evaporation occurs inside the liquid when the vapor pressure = atmospheric pressure
Temperature
= A measure of the average KE of atoms and molecules in a system - Kelvin (K) temperature scale is proportional to this - When KE doubles, the K temperature doubles
Covalent Network Solids
= Always composed of 1 or 2 nonmetals held together by networks of covalent bonds = C group elements often form covalent networks solids, as they can form four covalent bonds = Very high melting points and normally very hard, as atoms r covalently bonded with fixed bond angles
triangleHfus for Ionic Compounds
= As ionic bonds r much stronger than intermolecular forces, the triangleHfus values for ionic compounds r very large = melting and boiling temperatures for ionic compounds r very high
PV/RT vs P for 1.0 mole of N2(g) at Different Temperatures
= As the T increases, behavior N gas approaches that of an ideal gas • Gas only behaves ideally at P below ~ 5 atm
Crystalline Solids
= Atoms, ions, or molecules r arranged in an orderly fashion that follows a pattern of repetition in 3D - Segments that repeat in 3D r called unit cells = Macroscopic structures usually have flat surfaces that make definite angles to one another = Quartz and ionic solids r crystalline
Maxwell-Boltzmann distribution, Temperature and Pressure
= Average KE of the particles in a system increases as the temperature increases - At any temperature, there is a large range of KE = At any given temperature, the particles with less KE exert a lower pressure and the particles with more KE exert a higher pressure - Total pressure exerted by the gas particles in a system in an average
Boiling Points of Water
= Boiling points decrease as elevation increases (higher altitude)
Metallic Solids
= Bonding is not covalent - Not enough e-s to fill octet = Bonding results from the attractions btwn nuclei and delocalized Ve- moving throughout the structure = Bond strength increases as # of bonding e-s increases
Properties of Ionic Solids - Cleave along planes
= Brittle 3D structure = Ions line up in a repetitive pattern that maximizes attractive forces and minimizes repulsive forces = Not malleable or ductile
Reactions Rates and Temperature
= Collision rates increase as temperature increases - When temp. increases, the average kinetic energy of the particles in that system increases • This increases the average velocity of the particles (KE = 1/2 mv^2) - The collision rate increases as velocity increases • This rule is amplified when the reactants r gases, but it's also true for other states - Increases in temp. increase the value of the rate constant, k, which the rate for any rate law
Reactions Rates and Surface Area
= Collision rates increase as the surface area of reactants in the solid phase increases - When u break something in half, the total surface area increases - If the object is ground into a powder, the total surface area of the particles is much larger than the surface area of the original object - When the surface area increases, a larger # of reactants in the solid phase r able to collide with the other reactants
Reactions Rates and Concentration
= Collision rates increases as the concentration of reactants in the liquid or gas phase increases - If there r more reactants in a liquid or gaseous system of the same volume and temperature, there will be more collisions btwn reactants per unit of time - Reaction rates increase when collision rates increase for all processes that r higher than 0th order rate = k rate = k[A] rate = k[A]^2
Kinetic Molecular Theory 4
= Collisions experienced by gas particles r elastic • KE is conserved
Explain how absorption of electromagnetic radiation occurs in infrared (IR) spectroscopy experiments
= Different types of covalent bonds in molecular vibrate at different frequencies, which r within the IR spectrum, and IR radiation of the exact same frequency is absorbed by those covalent bonds
Explain how Einstein was able to use experimental evidence related to the photoelectric effect to conclude that quantized energy must be contained by individual particles
= E-s don't eject until the threshold frequency is reached, even after prolonged exposure • This would lead us ti believe that there is a one to one relationship btwn the e- and another particle • If it was not one to one, e- would slowly absorb enough energy to break free from the metal's surface = Once the threshold frequency is reached, ejections take place immediately • This further supports the idea that an e- absorbs a single particle containing a set quantity of energy • If they slowly absorbed continuous energy, ejections wouldn't take place immediately = At a set frequency, velocity of all ejections is the same; however, increasing the frequency increases the velocity of the ejections • Further supports the one to one relationship of e- to photon = For there to be a one to one relationship, photons must be particles
Covalent Network Solids (Graphite)
= Each C forms 3 sp^2 hybrid orbitals that bind with 3 other C atoms = These sheets sit on top of one another = Delocalized pi-bonds btwn sheets = Weak Pi-bonds and LDF allow sheets to slide over one another = If hooked up to a potential difference, e-s will flow = High melting point, as covalent bonds btwn C in each layer r relatively strong
What factors r necessary in order to cause an e- transition during an ultraviolet/visual (UV/Vis) spectroscopy experiment?
= Energy contained by the incident photons must be exactly the same as the difference in energy btwn the 2 MOs in order for the photons to be absorbed by e-s and transmit the e-s to the higher energy MO • Molecule must have Pi-orbitals (which means that it must contain double or triple bonds within its structure) or it must have non-bonding MOs (which means it must contain MOs with LP) • Light btwn the wavelength of 200 nm and 800 nm can only transmit e-s from pi (bonding orbitals) to Pi+ (anti-bonding orbitals), or from non-bonding orbitals to a pi+ (anti-bonding orbitals) or sigma+ (anti-bonding orbitals)
Avogadro's Principle
= Equal volumes of different gases at the same temperature and pressure contain equal numbers of particles • Each balloon contains different types of gaseous particles at 0*C and 1 atm • However, they all contain 6.7x10^-2 moles of gaseous particles
Species with more electrons and larger electron clouds are more polarizable
= Have a weaker hold on their outer electrons = When moving down a group, or constructing molecules with more atoms, the resulting species has more e-s - More e-s a species has, the more polarizable it is - This is not always true when moving from left to right across a period, as atomic radius and therefore the size of the e- cloud decreases
Limiting Reactant vs Excess Reactant
= If u have set quantities of 2 different reactants, one will get used up and some amount of the other will be leftover - Limiting • reactant that used up limits how far the reaction will proceed - Excess • reactant that is leftover when reaction is complete
Explain how solutes can be separated through paper chromatography based in intermolecular forces
= In paper chromatography, the bottom of a strip of chromatography paper is placed in the solution in question • Solution is drawn up the paper due to capillary action • stationary phase is the chromatography paper, and the moving phase is the solvent used. • As solvent moves up the piece of paper it carries solute particles with it • However, distances that the different solute particles travel up the paper depends on their relative attractions for the moving solvent and the stationary paper = Paper is made of cellulose fibers, which have polar and non-polar components • Cellulose fibers have non-polar C chains with polar -OH groups that stick out at various locations along the structure • Solutes that r considered to be "most polar" can form H-bonds at several locations on their structures • These structures will have a greater attraction for the stationary paper than they do for the mobile mostly non-polar solvent = If there r strong intermolecular FoA btwn the solvent and solute, it will travel a fairly far distance up the paper • If there t weak intermolecular FoA btwn the solvent and solute, solute will fall out of solution and cling to the paper fairly close to the solution's surface • All identical solute particles will fall out if the solution and be deposited on the paper at the same height, but this height will be different for different types of solute particles • As the different solute particles r often different colors, experiment produces different colored stripes at different heights above the surface of the solution • Pure solvent will always travel further up the paper than any of the solutes it originally contained
Molecular Solids
= Molecular shape plays a role in their physical state - Saturated and unsaturated fat = In a solid, molecules r held close together in a regular pattern by intermolecular forces that attempt to maximize attractions and minimize repulsions
Molecular Liquids
= Intermolecular forces also attempt to maximize attractions and minimize repulsions = These forces r strong, but not as strong as they r in a solid, so the molecules have more freedom to move
Vapor Pressures of Ionic Solids
= Ionic compounds have very low vapor pressures and very high boiling points - Strong Coulombic interactions btwn cations and anions
Would it be possible to conduct an UV/Vis spectroscopy experiment on a solution containing a colored compound? Justify
= It is possible to conduct UV/Vis spectroscopy experiments on solutions containing colored compounds, as all colored compounds absorb light in the visual spectrum
Would it be possible to conduct an UV/Vis spectroscopy experiment on a solution containing a colorless compound? Justify
= It is possible to conduct UV/Vis spectroscopy experiments on solutions containing colorless compounds, as some colorless compounds absorb light in the ultraviolet spectrum
aminopropane, CH3CHNH2CH3, and isobutane, C4H10 • Identify the types of intermolecular forces that exist in a pure sample of aminopropane • and isobutane
= LDF and H-bonds - H atoms bonded to highly electronegative N atom, which has a LP of e-s = Non-polar so only LDF
Covalent Network Solids (Diamond)
= Many C atoms bound together with sp^3 hybrid orbitals = Each C makes a single covalent bind with 4 other C atoms = Very hard and very high melting point (3550 Degrees C)
Molecular Shape and Dispersion Forces
= Molecular shape plays a role in the strength of LDF and physical state - Saturated fat, straight, solid at room temp - Unsaturated fat, bent, liquid at room temp = Dispersion forces increase as contact area btwn molecules increases
Properties of Molecular Solids
= Most don't conduct electricity when molten or dissolved in water - Individual molecules have no net charge, as Ve- r tightly held within covalent bonds and LP - Acids r molecules that can ionize and conduct electricity = Most molecular solids r held together by intermolecular forces, which r much weaker than ionic or covalent bonds - Have much higher vapor pressures than ionic solids - Have much lower melting and boiling points than ionic solids
Properties of Ionic Solids - Solubility and Conductivity
= Most r soluble in polar solvents = Conduct electricity only when molten or dissolved in a polar solvent, as the charged particles r free to move - Higher the concentration of ions in a solution, higher the electrical conductivity
Particulate Characteristics of Solids
= Motion of individual particles is limited - Particles don't undergo translation with respect to one another = Particles r very close together = Structures r held together by intermolecular forces and/or chemical bonds = Structure is influenced by the ability of the particles to pack together
Net Ionic Equation vs Complete Ionic Equations
= Net - only shows the reaction that actually took place - Normally used when dealing with a problem that only involves the precipitation reaction = Complete - Shows all of the species that r present - Normally used when it is necessary to identify all of the species in a system (reacting species and spectator ions)
Metallic Bonding - Electron Sea Model
= Nuclei and inner core e-s r localized, while Ve- r free to move throughout the solid 1. Conduct electricity 2. Conduct Heat 3. Malleable and Ductile - Lack directional bonds
Redox Titrations
= Often used to determine the concentration of a species that can be oxidized in a solution • A solution with a known concentration of a species that is easily reduced is added to a solution with an unknown concentration of a species that will be oxidized in the reaction • A color change signals the arrival at the endpoint, which is extremely close to the equivalence point = Equivalence Point • Occurs when equal # of moles of the species being oxidized and the species being reduced have reacted = Titrant • + to solution
Protein Function
= Overall surface shape determines function = Groove creates the opportunity for a protein to interact with other molecules = Enzymes break down other molecule through this type of interaction = Water soluble proteins have polar 'R' groups that face out and non-polar 'R' groups that face in - H-bonds form with water - LDF between side chains on the inside
Explain why bubbles of CO2 (g) form when u open a bottle of soda
= Partial P of CO2(g) in the neck of the bottle is 4 atm. • If the system is at 25'C, it will maintain a constant concentration of 0.1 M CO2 in the solution • When the lid is removed, the equilibrium shifts • The system then contains more aqueous CO2 than it will allow with the reduced partial P of CO2 (g) on the surface of the liquid • In response to this, CO2 (g) bubbles form and the excess CO2 starts to leave the solution = If u leave the lid off the bottle for long enough, system will re-establish its equilibrium with a smaller concentration of aqueous CO2 (9.9x10^-6 atm)
Properties of Liquids
= Particles r constantly moving and colliding with one another - Particles undergo translation with respect to one another - Movement is influenced by the strength of the intermolecular forces that r present btwn the particles and the Temp = Particles r very close together
Explain what happens within the structure of a molecule during an ultraviolet/visual (UV/Vis) spectroscopy experiment
= Photon absorbs an e- for a pi (bonding orbital) and transmits it to a pi+ (anti-bonding orbital); or a photon absorbs an e- from a non-bonding MO and transmits it to a pi+ (anti-bonding orbital or sigma+ (anti-bonding orbital) • Photon must contain the same amount of energy as the difference in energy btwn the 2 MOs
Synthetic Polymers - Polyethylene
= Plastic r non-polar, so they r held together by LDF = LDF hold chains together
Properties of Synthetic Polymers
= Plastics r generally flexible solids or viscous liquids = Heating plastics increases flexibility and allows them to be molded - Molecular vibrations increase - LDF weaken = Properties of synthetic polymers can be modified by manipulating their structures
Identify the CA/CB pairs in following reactions b) C3HOOH + H2O <—> CH3COO- + H3O+
A B CB CA CH3COOH and CH3COO- r C acid base pair H2O and H3O+ r a C acid base pair
Pi-bonds and Polarizability
= Presence of pi-bonds increases polarizability = e-s in pi-bonds r more delocalized, and thus, have more freedom to move and assist with the polarization of the species
ethanol, C2H4O, and acetic acid, CH3COOH • Identify types of intermolecular forces that exist in a pure sample of acetic acid • Highest boiling point??
= Pure acetic acid has LDF and H-bonds • also have some ion-dipole = Acetic acid, LDF in both structures r similar, but acetic acid forms H-bonds which r much stronger than the dipole-dipole forces btwn ethanol molecules • as greater amount of energy is required to break stronger FoA, the boiling pt of acetic acid is higher
Amorphous Solids
= Random arrangement of particles = Particles have no orderly structure = Macroscopic structures lack well defined faces and shapes = Many r mixtures of molecules that don't stack up well together = Glass and rubber r examples of amorphous solids
Reaction Orders (m and n)
= Reaction orders cannot be predicted from the balanced equation = There r only found through experimental data = Reaction orders may be: • Zero Order • First Order • Second Order meaning that m and n may be 0, 1, or 2
Reaction Rates r Influenced by Collision Rate and Catalysts
= Reaction rates increase in the presence of a catalyst = Reaction rates increase when collision rates increase = Collision rates increase 1) as the concentration of reactants in the liquid or gas phase increase 2) as the surface area of reactants in the solid phase increases 3) as temperature increases = Not every collision triggers a chemical reaction
Charles' Law
= Relationship btwn Temperature and Volume of Gases V1/T1 = V2/T2 - V is proportional to Temp - must use absolute Temp (K)
Photoelectric effect
= Science world knew that certain clean metal surfaces would shed e-s when certain frequencies of light were shined on them • 1st Fact: Highly intense low frequency light doesn't eject any e-s, even if it shines on the surface for several days • 2nd fact: When threshold frequency is reached, e-s r ejected immediately • 3rd fact: Increasing the intensity of the light at a frequency that will cause e-s to eject results in a higher ejection rate. However, all rejected e-s share the same velocity • 4th fact: Increasing the frequency of light increases the velocity of the ejected e-s. However, all ejected e-s share the same velocity
Sublimation
= Solids can evaporate and have a vapor pressure = As intermolecular forces r stronger in solids, the vapor pressures of solids r normally low = Solids with high vapor pressures, have relatively weak intermolecular forces
Gas solubility and temperature
= Solubility of most gases decreases as temperature increases • Gases tend to have weak intermolecular forces - N2 and O2 form weak dipole-induces dipole forces and weak dispersion forces with water • As the kinetic energy of particles within a solution increases, aqueous particles break free from these weak attractions and re-enter the gas phase
One of the factors that influences the rate of any chemical reaction is the collision rate of the reactants a) Identify the variable that influence the rate at which reactants collide and explain how each of these variable can increase the rate of a chemical reaction
= Temperature - is a measure of the average KE of the particles in a system. When temp. incr., average KE of reactants incr.. KE = 1/2 mv^2, so as average KE incr. average velocity of the reactants also incr.. When velocity of reactants incr., # of collisions per unit time incr. = Concentration of reactants - When more reactants per unit vol., and temp. remains same, # of collisions per unit time incr. = Surface Area of reactants - As particle size incr., SA decr.. When break something in half, total SA incr.. If object is ground into powder, total SA of particle is much larger than the SA of the original object. When SA incr., larger # of molecules in solid phase r able to collide w/ the other reactants per unit of time
PE, Polarity, and Strength of Intermolecular Forces
= The PE of e-s associated w/ - pole of a molecule decreases as approach + pole of another molecule = Molecules w/ stronger dipoles have stronger attractions for one another, which pull them closer together - PE decreases as molecules move closer together = Energy must be added to weaken or break intermolecular forces - PE increases as molecules move away from one another
Kinetic Energy of Gas Molecules
= Transitional Energy - Gas molecules move through space in straight lines = Rotational Energy = Vibrational Energy = Most of a gas particle's KE is related to its translational velocity
If u were to design an experiment to find the concentration of a compound in solution, would u choose to use an infrared (IR) spectrometer or an ultraviolet/visual (UV/Vis) spectrometer? Justify
= Ultraviolet/visual (UV/Vis) spectrometer • If molar absorptivity, a, of the compound at the wavelength being used in the experiment is known, one can use an UV/Vis spectrometer to measure the absorbance, A, of a sample of the solution • Concentration of the solutions can then be calculated using the Beer-Lambert law equation: A = Ebc • In this equation, 'b' is the oath length of the curvette, which would be known, and 'c' is the concentration of the solution
If u were to design an experiment to determine the differences btwn some of the energy levels in a pure sample of a molecular compound, would u choose to use an infrared (IR) spectrometer or an ultraviolet/visual (UV/Vis) spectroscopy? Justify
= Ultraviolet/visual (UV/Vis) spectrometer • In this, photons cause e-s to more from lower energy MOs to higher energy MOs • For this to happen, the difference btwn the energy levels of the 2 MOs must be exactly the same as the energy contained by the photon • After one had determined the frequencies of electromagnetic radiation that r being absorbed by the sample, the energy contained by the photons in that electromagnetic radiation can be calculated using E=hv
Boiling Points of Different Liquids
= Vapor Pressure on the surface of a liquid depends on the strength of its intermolecular forces - A molecule restrained by strong intermolecular forces requires more energy to break free from the liquid state - When a system requires more energy to cause its molecules to enter the gas phase, it will also require more energy to cause its vapor pressure to = the atmospheric pressure
Biomolecules - Protein Structure
= Very long chains can be constructed through the reaction from the previous slide = Chains may contains hundreds of amino acids = H-bonds form btwn Os, and Hs that r bonded to Ns, within the same chain = Following secondary structures can form - a-helix structure is held together by H-bonds - B-pleated sheet structure is also held together by H-bonds = Tertiary structures r caused by intermolecular interactions btwn R groups = Quaternary structures r caused by intermolecular interactions btwn different chains
Properties of Ionic Solids - Strong Bonds
= Very strong Coulombic FoA btwn cations and anions - High melting points - Very hard - Low volatility
Beverages and Pollution
= Warm carbonated drinks go flat faster than cold carbonated drinks = Thermal Pollution • During many industrial processes, water is pumped out of lakes or rivers and used to cool equipment, gases, or other liquids • Heat flows into this water • Then returned to the lake or river that it came from • Temperature of that body of water increases, (O2 (aq)) drops, and the fish die
Orientation and Dipole-Dipole
= When + and - dipoles line up well, attractive forces r stronger and repulsive r weaker = When + and - dipoles do not line up well, attractive forces r weaker and repulsive r stronger
Vapor Pressure
= When molecules leave the surface of a liquid to enter the gas phase, they exert a pressure = Vapor pressure exerted depends on the rate of evaporation per unit area of the liquid's surface = Rate of evaporation and vapor pressure increase as temperature increases = When 2 substances r at the same temperature, rate if evaporation and vapor pressure will be higher in the substance that has weaker intermolecular forces
Mass % Element Mass % Component
= [(#of atoms of element)(element's atomic mass)] / [(Formula weight of compound)] x100 = (mass of component in question) / (total mass of substance) x100
Explain why every element has a distinct atomic emission spectrum
= amount of energy possessed by the e-s of an element is fixed according to its principle energy levels and sublevels • Change in energy that an e- experiences when it drops from a higher to a lower energy level is also fixed • This means that the energy possessed by a photon that is emitted when an e- drops from a higher to a lower energy level is also an exact quantity • As the energy levels possessed by different types of elements r different (due to different nuclear charges and different #s of energy levels and sublevels), the changes in energy that the e-s experience as they drop from higher to lower energy levels r also different • This means that the energies contained in the photons emitted by different elements r different, so the wavelength (color) the light is also different
dipole-induced dipole
= attractions resulting from these forces r stronger when magnitude of dipole in polar molecule is larger - Molecules that have larger dipoles have greater ability of induce a larger dipole in a non-polar molecule = Strength of these forces increases when non-polar molecule has larger e- cloud and is more polarizable
What is the difference btwn a continuous spectrum and an atomic emission spectrum?
= continuous spectrum contains every possible wavelength • Rainbow is an ex. of a continuous spectrum of visible and each color blends into the next • Color gradually changes as the wavelength of light changes • If rainbows were missing certain wavelengths of light, they would have transparent bands that r devoid of color • Every element has a distinct atomic spectrum and in an atomic spectrum, only certain wavelengths of light r present, so atomic spectrums don't possess every possible wavelength of light
Would it be possible to conduct an UV/Vis spectroscopy experiment on a sample of the compound? Justify H-C=C=C-OH II I O H
= would be possible to conduct a UV/Vis spectroscopy experiment on a sample of this compound, as it has pi-orbitals associated with its double bonds and non-bonding MOs (LP) • Light btwn the wavelength of 200 nm and 800 nm can only transmit e-s from pi (bonding orbitals) to pi+ (anti-bonding orbitals), or from non-bonding orbitals to a pi+ (anti-bonding orbitals) or sigma+ (anti-bonding orbitals)
Atomic mass =
=(a1)(%1) + (a2)(%2) +...
Electronegativity: Reasoning
=Electronegativity increases as atomic radius decreases -When 2 atoms r involved in a chemical bond, bonding e-s will experience a greater attraction for the + nucleus that is closest to them.
First Ionization Energy: Reasoning
=Generally increases as atomic radii decrease -According to Coulomb's Law, force of attraction decreases as distance between e-s and protons increases
Label acid, base, conjugate acid, and conjugate base i) HClO4 + H2O —> ClO4- + H3O+
A B CB CA
Ionic Bonding Defined
=Metals transfer e-s to non-metals, and 2 form bonds due to electrostatic attractions between them (Coulomb's Law) -or... =Cations and anions form electrostatic bonds based on opposite charges. Cations and anions may be polyatomic
Ionic Radius: Cations (Across Period from Left to Right)
=Radii of cations decrease -# of e-s remains same and protons added -Shielding effect experienced by outer e-s of cations in period similar, so addition of protons increases effective nuclear charge on those e-s. -According to Coulomb's Law, increase in + charge increases force of attraction experienced by each e-, thereby decreasing radius
First Ionization Energy: Exceptions
=Requires more energy to pull up e- from full d-subshell than it does to pull the only e- in a p-subshell (when in same period). =Requires more energy to pull up e- from full s-subshell than it does to pull the only e- in a p-subshell (when in same period). -That single e- is easier to remove, bc only e- in higher energy subshell, and being "shielded" by electrons in lower energy shells
Electron Affinity: (Across Period from Left to Right)
=Ve- r in same shell -Shielding effect experienced by outer e-s of elements in a period similar so addition of protons increases effective nuclear charge of those e-s =More protons r added and atomic radii decrease. -According to Coulomb's Law, increase in + charge and decrease in atomic radii increase force of attraction experienced by added e-
Atomic radius (Across a Period from Left to Right)
=Ve- r in same shell -Shielding effect experienced by outer e-s of elements in period r similar so addition of protons increases effective nuclear charge on those electrons =Moving from left to right, more protons are added. -According to Coulomb's Law, increase in + charge increases force of attraction experienced by each e-, thereby, decreasing radius.
Ionic Radius: Anions (Across Period from Left to Right)
=When u encounter 1st anion, radius increases dramatically -Repulsions from additional e-s cause e- cloud to expand =Radii then continue to decrease -Shielding effect experienced by outer e-s of anions in period similar so addition of protons increases effective nuclear charge on those e-s -According to Coulomb's Law, increase + charge increases force of attraction experienced by each e-, thereby decreasing radius
Multistep Reaction Energy Profiles
A + B —> AB (Step 1) AB + CD —> ABC + D (step 2) === A + B + CD —> ABC + D (overall) Step 1 A + B —> AB Step 2 AB + CD —> ABC + D
Kinetics
A + B —> D + E 1) Rate of disappearance of a reactant Rate(A) = -delta[A] / delta t (- sign needed, as rates r always + values) 2. Rate of appearance of a product Rate(D) = delta[D] / delta t = rate at which 1 species appears or disappears can be used to find other rates aA + bB —> dD + eE
Beer-Lambert Law
A = Ebc A = absorbance E = molar absorptivity (1/Mcm) b = path length of sample (cm) c = concentration (M) • E describes how intensity a sample of ions or molecules absorbs light at a specific wavelength • In most experiments, path length and wavelength remain constant, so E also remains constant, and absorbance, A, is only proportional to concentration, c
Label acid, base, conjugate acid, and conjugate base a) HNO3 + H2O <—> H3O+ + NO3-
A B CA CB
Label acid, base, conjugate acid, and conjugate base d) HF + H2O <—> H3O+ + F-
A B CA CB
Label acid, base, conjugate acid, and conjugate base f) HCN + H2O <—> H3O+ + CN-
A B CA CB
Identify the CA/CB pairs in following reactions a) HF + H2O <—> H3O+ + F-
A B CA CB HF and F- r C acid base pair H2O and H3O+ r C acid base pair
Label acid, base, conjugate acid, and conjugate base b) HCO3- + OH- <—> CO3- + H2O
A B CB CA
Solution
A homogeneous mixture of two or more substances
Acid-Base Catalysis
A reactant gains or loses a proton, which forms a new intermediate
Use Coulomb's law to explain why this electron has the lowest ionization energy.
According to Coulomb's Law, F=k (q1q2)/d^2, the force of attraction between 2 charges particles decreases as the distance between them increases, as distance is the denominator of the equation. As you can see from the shell model above, the e- that was identifies as having the lowest ionization energy is the furthest from the nucleus. When the force of attraction decreases, the energy required to remove the e- also decreases.
Two separate pure samples of CO2 were analyzed. Both samples were found to contain 27.29% C by mass. Justify these findings on the basis of atomic molecular theory.
All CO2 molecules contain exactly 1 C and 2 O atoms. Although different isotopes of C and different isotopes of O have different masses, the ratio of isotopes of C and the ratio of isotopes of O in any pure sample of CO2 is constant. If we could calculate the average mass of all the atoms of an element in a pure sample, we would obtain the average atomic mass of that element, which is given on the periodic table. As the ratio of C atoms to O atoms in both pure samples is the same, the ratio of the masses of C atoms to O atoms in that pure sample will also be the same.
Solubility Rules
All salts containing: Group IA, NH4+ (Ammonium), NO3- (Nitrate), CH3COOH- (Acetate)
Elementary steps that involve 3 or more reacting species r very rare. Explain why this is.
All termolecular elementary steps r very rare, as they require the simultaneous collision of 3 particles with correct orientations and enough energy. Elementary steps that require the simultaneous collision of more than 3 reactant particles r very rare for the same reason
On average, e- from the 2s subshell of a element are further from the nucleus than e- from the 2p subshell of an element; however, the energy required to remove an e- of an element from 2s is greater than that of 2p. Explain!
Although the average distance between the nuclues and an e- in 2s is greater than that of an e- in 2p, electrons in 2s spend some of their time much closer to the nucleus than those in 2p. As a result, e- in 2p experience a greater shielding effect. The greater repulsive forces that the 2p e- experience from the 1s e- result in a lower activation energy for the 2p e-.
What is the only polyatomic cation you need to know??
Ammonium (NH4 +)
Electronegativity
An elements ability to attract e-s in a chemical bond
Which atoms has the smallest radius? Na vs Ar. Justify
Ar, bc Ve- of both elements r in same shell (n=3). Thus, shielding effect experienced by outer e-s of both elements similar -Na has 11 protons in nucleus, as it is neutral and has 11 e-s. Ar has 18 protons in nucleus, as it is neutral and has 18 e-s. -Addition of protons increases effective nuclear charge on Ve-s -According to Coulomb's Law, increase in + charge increases force of attraction experienced by each e-, thereby decreasing radius. This gives Ar a smaller atomic radius.
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces e. He and Ar
Ar, bc both LDF but Ar is larger and has more e-s, making it more polarizable than He • Ar experiences greater LDF • As a greater amount of energy is required to break stronger FoA, boiling pt of Ar is higher
The __________ given to you on the periodic table is an average of all the isotopes of that element. The __________ of any large number of atoms of a given element is always the same for that given element. The ratio of isotopes for each given element is constant.
Atomic mass Average mass
Expanded Octets
Atoms in period 3-7 can bond with other atoms in such a way that they end up with more than 8 e-s in their octets -this is bc the d-orbitals r empty which means they can be used during bonding
Label acid, base, conjugate acid, and conjugate base c) H2PO4- + H2S <—> H3PO4 + HS-
B A CA CB
Label acid, base, conjugate acid, and conjugate base e) CN- + NH4+ <—> HCN + NH3
B A CA CB
Trigonal Planar Ex. - Charge Clouds - Bonds - Lone Pairs - Bond Angle - Hybridization -
BF3; 3; 3; 0; 120 degrees; sp^2
Which atom in each set has the larger radius? a) Be or O b) Cu or Br c) F or I d) O or As e) Kr or K f) Ba or Li
Be, Cu, I, As, K, Ba
Is H2O polar or non-polar?? Explain by discussing shape, polar bonds, and whether or not dipoles cancel
Bent so 2 H-O bonds and 2 lone pairs - Polar individual bonds bc O is more electronegative than H - Polar overall compound bc dipoles don't cancel due to asymmetrical arrangement of 2 O-H bonds - O end is slightly - and H ends r slightly +
Is ozone polar or non-polar?? Explain by discussing shape, polar bonds, and whether or not dipoles cancel
Bent so 2 O-O bonds and 1 lone pair - non-polar individual bonds bc electronegativity difference in an O-O bond is zero - Therefore, non-polar overall compound, as there r no dipoles
Which is most bond in each set? Explain a. C-F or C-O b. P-O or P-F c. As-S or As-F
C-F; P-F; As-F; greater electronegativity difference, the more polar the bond
explain why propane, C3H8, is a gas and decane, C10H22, is a liquid at 25'C and 1 atm
C10H22, both non-polar and only LDF but C10H22 is larger and has more e-s, making it more polarizable than C3H8 • C10H22 experiences greater LDF • Bc of stronger FoA, C10H22 exists as a liquid at 25'C and 1 atm, while C3H8 exists as a gas
C2H2 or C2H6 H-C=_C-H or 2 C surrounded by 6 H w/ single bonds a. What is the bond order for the C-C bond in each structure
C2H2 = 3 C2H6 = 1
C2H2 or C2H6 H-C=_C-H or 2 C surrounded by 6 H w/ single bonds b. Which structure has the shortest C-C bond length? justify
C2H2 bc has single bonds - triple bonds have greater e- densities between bonding atoms than single bonds - Greater e- density between bonding atoms increases force of attraction between protons of each nucleus and centrally located bonding e-s which shortens bond length
C2H2 or C2H6 H-C=_C-H or 2 C surrounded by 6 H w/ single bonds c. Which structure has the greatest C-C bond energy? Justify
C2H2 bc has single bonds - triple bonds have greater e- densities between bonding atoms than single bonds - Greater e- density between bonding atoms increases force of attraction between protons of each nucleus and centrally located bonding e-s which shortens bond length - Force of attraction is greater, energy required to break bond is also greater
which species has the highest boiling point? C2H6 or C3H8
C3H8 bc although both non-polar (LDF), larger molecule has higher boiling point bc more polarizable
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces n. C2H6 or C4H10
C4H10, bc both LDF but C4H10is larger and has more e-s, making it more polarizable than C2H6 • C4H10 experiences greater LDF • As a greater amount of energy is required to break stronger FoA, boiling pt of C4H10 is higher
explain why ethane, C2H6, melts at -183'C and nonane, C9H20, melts at -54'C
C9H20, both non-polar and only LDF but C9H20 is larger and has more e-s, making it more polarizable than C2H6 • C9H20 experiences greater LDF • Bc of stronger FoA, C9H20 exists as a liquid at 25'C and 1 atm, while C2H6 exists as a gas
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces d. CH4 and CCl4
CCl4, bc both LDF but I2 is larger and has more e-s, making it more polarizable than CH4 • CCl4 experiences greater LDF • As a greater amount of energy is required to break stronger FoA, boiling pt of CCl4 is higher
Explain why standard enthalpy of vaporization, DeltaH(vap), values for each set of compounds below rn't the same a. CH4 and H2O
CH4 has LDF and H2O has LDF and H-bonds • bc intermolecular FoA in these 2 substances r different, their enthalpies of vaporization will also be different
Tetrahedral Ex. - Charge Clouds - Bonds - Lone Pairs - Bond Angle - Hybridization -
CH4; 4; 4; 0; 109.5 degrees; sp^3
CO2 or CS2 O=C=O or S=C=S a. Which structure has the shortest bond length between the central and each terminal atom? Justify b. Which structure has the greatest bond energy in its individual bonds? justify
CO2 and CO2 - Both held together by double bonds but S has larger atomic radius bc of another shell - S has larger radius than O, the distance between nuclear centers in the C-S bond is greater than the distance between nuclear centers in the C-O bond - bc of this, O's nucleus is closer to shared e-s than is S's nucleus - A closer proximity to shared e-s allows for a stronger force of attraction between protons and bonding e-s - When force of attraction is greater, more energy is required to break the bond
Linear Geometry Ex. - Charge Clouds - Bonds - Lone Pairs - Bond Angle - Hybridization -
CO2; 2; 2; 0; 180 degrees; sp
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces k. CaOH or H2O
CaOH, bc has LDF and H-bonds but CaOh had ionic bonds • Ionic bonds r much stronger than H-bonds • As a greater amount of energy is required to break stronger FoA, boiling pt of CaOH is higher
Which species has a smaller radius: Ca or Ca^2+? Provide an explanation and justify ur claims using your knowledge of atomic structure.
Ca^2+ -Both have same # of protons, but Ca^2+ has 2 less e-s which causes protons to pull on e-s in Ca^2+ with greater force of attraction. -Ca^2+ has one less shell and Ca has e-s in n=4 shell and Ca^2+ only has e-s in n=3 shell (lost its 2 e-s in n=4 shell) -By losing n=4 shell, radius of Ca^2+ decreased dramatically -As there r fewer core e-s in Ca^2+ its Ve-s experience less of a shielding effect.
Ion Formation Metals lost e- to form ______ K --> ___ + ____ Non-metals gain e- to form _______ Cl + ___ --> _____
Cations; K+ + e- Anions; e- --> Cl-
Classify as a physical change, chemical change, or both. Justify by identifying the types of intermolecular or intramolecular forces that r involved in each processes and describing what happens to those forces while the processes r occurring. b) CO2(g) —> C(s) + O2(g)
Chemical change • Covalent bonds in the CO2 molecule r broken
Molecular Formulas
Chemical formulas that provide the actual number of each type of atom in molecule
Empirical Formulas
Chemical formulas that provide the relative number of each type of atom in molecule. (a ratio in simplest form)
Cis vs trans isomers
Cis-2-butune = Carbon chain follows the same side Trans-2-butune = Carbon chain follows opposite sides
Which bonds from each set is most covalent? Explain a. Cl-Cl or Al-F b. N-O or C-O c. Ca-O or N-O
Cl-Cl (electronegativity difference between like elements is 0); N-O; N-O; smaller electronegativity difference between two atoms, the more covalent the bond. This is bc e-s r more evenly shared
Chlorine gas is bubbled through a solution of potassium iodide. a. What is/are the spectator ion(s) in the reaction? b. Write the balanced oxidation half reaction.
Cl2 + 2I- → I2 + 2Cl- K+ 2I- → I2 + 2e-
Conjugate Acid-Base Pairs
Conjugate acid-base pair are: • Acid and its conjugate base • bade and its conjugate acid
Mixture
Contains particles of more than one type atom, formula unit or molecule.
Pure sample
Contains particles of one type of atom, molecule, or formula unit (e.g. an ionic solid such as NaCl)
According to ____________ the forces of attraction between electrons and the nucleus in n=2 are less than the forces of attraction between electrons and the nucleus in n=1
Coulomb's Law
Photoelectron Spectroscopy (PES) data indicated that ionization energy for an e- in 2s orbital of Ca is 42.7 MJ/mol and ionization energy for e- in 3s orbital of Ca is only 4.65 MJ/mol. Explain.
Coulomb's Law and shielding effect -According to Coulomb's Law, force of attraction between 2 charged particles decreases as distance between them increases, as distance is the denominator of equation (F=k(q1q2/d^2) -e- in 3s orbital r, average, furthest from nucleus than e- in 2s orbital. When force of attraction decreases, energy required to remove e- also decreases. -e-s in 2s orbital r shielded by e- in n=1, and e- in 3s orbital r shieded by e- in n=1 and n=2 shells. Shielding effect, caused by repulsion by inner core e-s, reduces force of attraction between e- and nucleus. As e- in 3s orbital r being repelled away from nucleus by more inner core e-s, their ionization energies r lower.
Kinetic Molecular Theory 3
Coulombic FoA or repulsion don't exist btwn gas particles in a system
Copper turnings are added to a solution of copper (I) nitrate. a. Write the balanced oxidation half reaction.
Cu + Cu2+ → 2Cu+ Cu → Cu+ + e-
What are the 3 polyatomic ions that end in -ide??
Cyanide (CN-), Hydroxide (OH-), and Peroxide (O2 2-)
1) Ionization energy _______ when moving down group in PT. 2) Ionization energy __________ moving left to right across period in PT
Decreases Increases
Ionic Radius
Distance from the center of an ion's nucleus to its outermost electron
Double and triple bonds - charge clouds = - Hybridization = - Sigma bonds = - Pi bonds=
Double: 3; sp^2; 1; 1 Triple: 2; sp; 1; 2
What is the difference btwn E(a) and Delta E?
E(a) - (activation energy) is the minimum amount of energy that is required for a reaction to occur Delta E - (change in energy) is the energy that is lost or gained in the chemical reaction. • It's the difference btwn PE locked up in the bonds of the reactants and the PE locked up in the bonds of the products • Most of the energy is lost or gained in the form of heat, delta H • Remaining portion of this energy change comes from the work done on or by the system, which is related to changes in pressure and volume that occur during the chemical reaction
Planck's equation
E=hv Energy per Quantum (J) = Planck's constant (6.63x10^-34 Js) x frequency (s^-1)
Planck and Einstein's formula
E=hv Energy per photon (J) = Planck's Constant (6.63x10^-34 Js) x frequency (s^-1)
2 separate 250.0 g pure samples of NaCl were analyzed. Both samples were found to contain 39.3% Na and 60.7% Cl by mass. Use what you have been learning about atomic molecular theory to explain why the same results would be obtained from both samples.
Each formula unit of NaCl contains exactly one Na and one Cl atom, so both samples have a 1:1 ratio of Na to Cl. The average atomic mass of Na would be the same in both samples, as the ratio of the different isotopes of Na would be the same. The average atomic mass of Cl would be the same in both samples, as the ratio of the different isotopes of Cl would be the same. Because all the above mentioned ratios are the same, the mass ratio between Na and Cl will also be the same in both samples.
Pauli Exclusion Principle
Each orbital can hold a maximum of two electrons that will spin in opposite directions
Determine Bond Type H (2.1) - H (2.1)
Electronegativity Difference = 0.0 Non-polar covalent
Determine Bond Type H (2.1) - Br (2.8)
Electronegativity Difference = 0.7 polar covalent
Determine Bond Type Li (1.0) - F (4.0)
Electronegativity Difference = 3.0 Ionic
S is more electronegative than Ca. Explain why this is and justify your claims using your knowledge of atomic structure
Electronegativity increases as atomic radius decreases. -Ve- in larger elements experience greater amount of shielding from inner core e-s than Ve- in smaller elements. -When 2 atoms r involved in chemical bond, Ve- will experience greater attraction for + nucleus that is closest to them -According to Coulomb's Law, forces of attraction increases as the distance between e-s and protons decreases.
Use 2 analogies to describe continuous change
Elevation - It can increase or decrease by infinitely small quantities Velocity - It can increase or decrease by infinitely small quantities
The reaction-energy profile diagram below outlines an uncatalyzed process Potential Energy ______________ / \ / \ l l / \ _________________/ \__________________ Reaction progress d) Is this process endothermic or exothermic? Explain.
Endothermic • bc PE contained within the bonds of the products is greater than that of the reactants • energy was absorbed from the surroundings during the reaction
A chemical reaction takes place in a beaker that u r holding. While the reaction is taking place, ur hand feels cold. b) Is the reaction endothermic or exothermic?
Endothermic • products contain more PE
Energy must always be added to remove electrons means are _______________. Values obtained by shining different frequencies light on pure sample of neutral atoms in gas phase, recording frequency that removes electrons and using E=hv to find 1st ionization energy
Endothermic process
Activation Energy (E(a))
Energy must be absorbed to contort or weaken bonds in reactant molecules so that they can break and new bonds form. • If E(collision) < E(a) the reaction will not happen • Reaction rates depend on the magnitude of E(a) — Generally a slower rate — Generally a faster rate, when at the same temperature • Generally, if less energy is required to get over the hump, more reactants will collide with enough energy
Enzymes
Enzyme binds to the reactant(s) to form a new reaction intermediate
Which species has a smaller radius: F or F-? Provide an explanation and justify ur claims using ur knowledge of atomic structure.
F -Both have same # of protons, but F has 1 less e- which causes protons to pull on e-s in F with greater force of attraction. -Addition of extra e- in F- causes greater electron-electron repulsion which increases distance between Ve- and increases its radius.
Ion-Dipole and Coulomb's Law
F = k (Q1Q2)/d^2 — Ion-Dipole FoA increase as: - Radius of the ion decreases - Charge of the ion increases - Magnitude of the dipole on the polar molecule increases
Ion-Dipole and Coulomb's Law
F = k(Q1Q2)/d^2 • Some ionic compounds don't dissolve in water • Solubility of ionic compounds can be explained through Coulomb's Law • If cation-anion attractions r stronger than ion-dipole attraction, compound won't be soluble • Ionic compounds don't dissolve in non-polar solvents as non-polar solvent don't carry permanent dipoles • However, ion-dipole FoA btwn Mg 2+ and water r stronger than those btwn Ba 2+ and water for same reason
What 2 elements don't double bond??
F and Cl
Which element from each set is most electronegative? a) F or C b) Al or Cl c) Po or S d) Cs or S e) Ca or Cl f) O or Se g) Zn or K h) C or Pb i) Ga or O
F, Cl, S, I, Cl, O, Zn, C, O
What is the strongest base in each following reactions? Justify based on solution equilibrium or FoA btwn particles d) HF + H2O <—> H3O+ + F-
F- is strongest base • HF is a weak acid, and weak acids have strong CB • Also know that F- is a relatively strong base, bc it's very electronegative • H2O has only moderate strength as a base, as it can act as an acids or a base
Solid iron (III) nitrate is added to water.
Fe(NO3)3 → Fe3+ + 3NO3-
Activation Energy E(a) AB + C <-> A + BC Forward Reaction vs Reverse Reaction
For - AB + C <-> A + BC Reverse - A + BC <-> AB + C The E(a) value changes for the reverse reaction
The electromagnetic spectrum is a continuous spectrum of light
Gamma Rays = V X-rays = I UV = B Visible light = G IR = Y Microwaves = O Radio = R
What charge do Group 4A elements acquire as ions?
Ge is 4+. Pb and Sn can be 2+ or 4+
Hydrogen gas is blown over hot lead (II) oxide. a. Explain your thought process about how to write the equation above.
H2 + PbO → Pb + H2O Hydrogen is already reduced as far as it can go, as such, it must oxidize. Now we need to think about what would get reduced. In this case, as oxygen is already reduced to O2- and cannot be reduced further, the lead will reduce to lead metal.
What is the strongest base in each following reactions? Justify based on solution equilibrium or FoA btwn particles a) HClO4 + H2O —> ClO4- + H3O+
H2O is strongest base • Strong acids (HClO4) experience ~100% dissociation and have weak CB • Thus, ClO4- is a weak base • H2O and ClO4- compete for H+ ions • H2O acquired H+ ions most of the time, as the reactions goes to completion
What is the strongest base in each following reactions? Justify based on solution equilibrium or FoA btwn particles b) HNO3 + H2O —> NO3- + H3O+
H2O is strongest base • Strong acids (HNO3) experience ~100% dissociation and have weak CB • Thus, NO3- is a weak base • H2O and NO3- compete for H+ ions • H2O acquired H+ ions most of the time, as the reactions goes to completion
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces g. H2O and H2S
H2O, bc both LDF but H2O has H-bonds and H2S has dipole-dipole forces • H-bonds r much stronger than normal dipole-dipole forces • As a greater amount of energy is required to break stronger FoA, boiling pt of NH3 is higher
Bent (2 lone pairs) Ex. - Charge Clouds - Bonds - Bond Angle - Hybridization -
H2O; 4; 2; <109.5 degrees; sp^3
"Big six" strong acids that completely ionize in water
HClO, HI, HBr, HCl, HNO3, H2SO4
What is the strongest acid in each of the following reactions? Provide justification based on solution equilibrium a) HI + H2O —> I- + H3O+ b) H2SO4 + H2O —> HSO4- + H3O+ c) HNO3 + H2O —> NO3- + H3O+
HI, H2SO4, and HNO3 r all very string acids • all 3 of the "Big six" strong acids • As they experience ~100% dissociation, equilibrium for these reactions lies very far to the right
Half Life for 1st Order Reactions
Half Life - The time it takes for the conc of a reactant to decrease by half • the half life for a first order reaction is a CONSTANT. plug in the half amount for the concentration to find the half life. = Deriving the half-life equation for 1st order processes • These equations can also be used for any radioactive decay problems, as those processes r always 1st order
IE_Li is less than ________ as large as IE_H+ If the most loosely held electron in Li was about the same distance from the nucleus as those in H and He, we would expect IE_Li to be about _______ times greater than IE_H+
Half; 3
John Dalton
He presumed that if elements were made of tiny indivisible particles, then molecules of a particular compound would always be composed of equal numbers of each type of element. Thus, each element in a given compound would account for a consistent percentage of that compound's mass. Ex. Water is always composed of the same number of H atoms and the same number of O atoms
In these experiments, ____ ______ _______ remove electrons from any shell, not just the outer shell. KE of ________ electrons is determined. Frequency of _________ is recorded.
High energy photons; ejected; photons
Great deviation from Ideal at _____ P and low T bc conditions _____ attractive forces btwn particles
High; max
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces a. Br2 and I2
I2, bc both LDF but I2 is larger and has more e-s, making it more polarizable than Br2 • I2 experiences greater LDF • As a greater amount of energy is required to break stronger FoA, boiling pt of I2 is higher
Explain why H2 is a gas and I2 is a solid at 25'C and 1 atm
I2, both non-polar and only LDF but I2 is larger and has more e-s, making it more polarizable than H2 • I2 experiences greater LDF • Bc of stronger FoA, I2 exists as a liquid at 25'C and 1 atm, while H2 exists as a gas
T-Shaped Ex. - Charge Clouds - Bonds - Lone Pairs - Bond Angle - Hybridization -
ICl3; 5; 3; 2; <90 degrees; sp^3d
Ionization energy for any electron is calculated using:
IE = hv - KE
Square Pyramidal Ex. - Charge Clouds - Bonds - Lone Pairs - Bond Angle - Hybridization -
IF5; 6; 5; 1; <90 degrees; sp^3d^2
If u were to design an experiment to identify an unknown compound, would u choose to use an infrared (IR) spectrometer or an ultraviolet/visual (UV/Vis) spectrometer? Justify
IR spectrometer • in this, different frequencies of electromagnetic radiation in the IR spectrum r absorbed by different types of bonds in the molecule that vibrate at the same frequencies • spectrum that is obtained from these experiments can be used to identify the different types of bonds in the structure and the elements that r involved in those bonds • spectrum for a compound also provides a 'fingerprint' that can be used to identify it
If u were to design an experiment to determine the different types of atoms and bonds that make up a pure sample of an unknown compound, would u choose to use an infrared (IR) spectrometer or an ultraviolet/visual (UV/Vis) spectrometer? Justify
IR spectrometer • in this, different frequencies of electromagnetic radiation in the IR spectrum r absorbed by different types of bonds in the molecule that vibrate at the same frequencies as the radiation • spectrum that is obtained from these experiments can be used to identify the different types of bonds in the structure and the elements that r involved in those bonds
FoA in Real Gases
Ideal Gas Law assumes there r no FoA btwn gaseous particles, but force is proportional to 1/d^6
Isotopes of an element exhibit ____________ behavior. This is why 1/1 H and 2/1 H will both bond with oxygen to form water. C-14 and C-12 bond with oxygen to form CO2.
Identical chemical
The energy profile diagram below was plotted for the following second order elementary reaction: A + BC <-> AB + C Potential Energy ______________ / \ / \ l l / \ _________________/ \__________________ a) At low temperature a relatively small fraction of collisions btwn reactants result in the formation of products. Describe the interactions btwn reactants that collided with an orientation that would produce products, but failed to do so
If 2 species collide with the correct orientation, but with insufficient energy, 2 molecules will bond together temporarily (A + BC —> A-B-C); however, they will not produce products • Instead, the temporary bonds will lose PE, and they'll once again separate reactants (A-B-C —> A + BC)
The table below outlines the results from 3 experiments, which were conducted at the same temperature, involving the following reaction Ex: [O2]initial [NO]initial Initial Reaction Rate 1 0.022 0.026 0.0256 M/s 2 0.022 0.013 0.0064 M/s 3 0.044 0.013 0.0128 M/s b) Which environmental factor could be altered in order to increase the initial reaction rate in experiment one if the initial conc. of the reactants remained the same? Justify
Increasing the temp. would incr. the initial reaction rate • By increasing temp., u r increasing the average KE of the molecules in that system • In doing so, u r increasing the average velocity of these particles • Collision rates incr. as molecular speed increases • This rule is amplified when when the reactants r gases, but it's also true for other states
Bohr called the shell __________, as each orbit was associated with quantized energy level
Integers quantum numbers
Steel — an ________ Alloy
Interstitial • C fills some spaces btwn Fe atoms • Interstitial C atoms make the lattice more rigid, less malleable, and less ductile • Retains a "sea of e-" so it can conduct electricity
Conducts electricity in molten state, dissolves water and is brittle. Molecule??
Ionic
Atoms from a pure sample of an element are ___________ and __________ through a magnetic field. Isotopes with smaller masses experience a greater degree of ____________
Ionized and accelerated; deflection
Equation for finding the number of orbitals and electrons??
Orbitals = n^2 Electrons = 2n^2
Write the equation for the 1st ionization of Potassium
K(g) --> K+(g) + e-
At -92'C, a pure sample of HBr has a higher vapor pressure than a pure sample of KBr b. Explain why the vapor pressure of HBr is higher than the vapor pressure if KBr at -92'C
KBr held together by ionic bonds, which r very strong, and HBr held together by dipole-dipole interactions, which r weaker • Bc FoA btwn particles in HBr r weaker, molecules or HBr can enter the gas phase more easily
Potassium bromide is least soluble in which of the 2 liquids from each set below. Justify c. NH3 or Br2
KBr is least soluble in liquid bromine, bc it's non-polar. Ionic compounds r soluble in polar solvents, and NH3 is a polar solvent
Potassium bromide is least soluble in which of the 2 liquids from each set below. Justify a. H2O or CH4
KBr is least soluble in methane bc it's non-polar. Ionic compounds r soluble in polar solvents such as water
Potassium bromide is least soluble in which of the 2 liquids from each set below. Justify b. CH3OH or CH3CH2OH
KBr is soluble in both CH3OH and CH3CH2OH, as they r both polar solvents. KBr is less soluble in CH3CH2OH bc it has a longer non-polar C chains
Which substance in each set has the highest melting pt? Justify ur answer using chemical principles a. KCl or SiO2
KCl has ionic bonds and SiO2 is a network solid held together with covalent bonds • Network solids t stronger than ionic bonds, so SiO2 will have a higher melting temperature
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces L. KCl or Cl2
KCl, bc has ionic bonds and Cl2 has LDF • Ionic bonds r much stronger than LDF • As a greater amount of energy is required to break stronger FoA, boiling pt of KCl is higher
KE per Gas Particle
KE = 1/2 mv^2 v = Velocity of a specific gas particle (m/s) m = mass of that particle (kg)
Molar Mass (w/ density) formula
MM = (D/P)•RT
The table below outlines the results from 3 experiments, which were conducted at the same temperature, involving the following reaction Ex: [O2]initial [NO]initial Initial Reaction Rate 1 0.022 0.026 0.0256 M/s 2 0.022 0.013 0.0064 M/s 3 0.044 0.013 0.0128 M/s h) If the same 3 experiments were conducted at a lower temperature, would the magnitude of the rate constant be greater than, less than, or equal to the value calculated above? Justify
Magnitude of rate constant would be less than the value calculated above • At lower temps., frequency of collisions btwn reactants is reduced • Also, average KE of of the reactants is less at lower temps., so fewer collisions would produce enough energy (activation energy) to cause a reaction • Thus, rate at which the reaction proceeds is reduced • As initial conc. would be the same, rate constant must have a smaller magnitude, as Rate=k[NO]^2[O2]
Expressing Concentration - 2 methods for expressing concentration
Molarity (M) = moles solute / liters solution • Molarity can change with temperature Mole fraction = X(A) = (moles A)/(moles A + moles B + ... + moles Z) • Mole fractions don't change w/ Temp
Calculating Mole Fractions
Mole Fraction - % composition by mikes of a single component in a mixture, represented in its decimal form X(A) = (Moles if 1 component (n(A)) in a mixture) / (Sum of moles of all components in mixture) X(A) = n(A) / [n(A) + n(B) + n(C) + n(D) + ... + n(Z)]
Rate Laws of Elementary Steps
Molecularity Elementary Reaction Rate Law Unimolecular A—>products Rate=k[A] Bimolecular A+A—>products Rate=k[A]^2 Bimolecular A+B—>products Rate=k[A][B] Termolecular A+A+A->products Rate=k[A]^3 Termolecular A+A+B->products Rate=k[A]^2[B] Termolecular A+B+C->products R=k[A][B][C] • Termolecular elementary reactions r very rareC as they require the simultaneous collision of 3 particles with sufficient energy and the correct orientations • Value of a rate constant, k, increases as temperature increases
Which bond from each set has the greatest bond energy? a. N-O or N-F b. B-F or B-Cl c. B-C or O-F d. C-O or C=O e. P-Br or P-Cl
N-F; B-F; O-F; C=O (Double bonds r shorter than single bonds and have greater bond energy); P-Cl Smaller atomic radius = smaller bond length = greater bond energy
Which bond from each set is the longest? a. N-O or N=O b. B-N or B-F c. Si-O or Si-I d. C-Cl or C-F
N-O (Single bonds r longer than double bonds); B-N; Si-I; C-Cl Bond lengths increase as the atomic radii increase
Explain why NH3 has a higher solubility in water than SbH3
NH3 is able to form H-bonds with water, whereas SbH3 is only able to form weak dipole-dipole attractions with water • Bc the intermolecular FoA btwn NH3 and water r stronger than those of SbH3 and water, water is able to hold a higher concentration of NH3
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces NH3 and CH4
NH3, bc both LDF and NH3 has H-bonds but CH4 is non-polar. • Both species r approximately same size, and H bonds much stronger than LDF • As a greater amount of energy is required to break stronger FoA, boiling pt of NH3 is higher
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces b. NH3 and NCl3
NH3, bc both LDF but NH3 has H-bonds and NCl3 has dipole-dipole forces • H-bonds r much stronger than normal dipole-dipole forces • As a greater amount of energy is required to break stronger FoA, boiling pt of NH3 is higher
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces i. NH3 and PH3
NH3, bc both LDF but NH3 has H-bonds and PH3 has dipole-dipole forces • H-bonds r much stronger than normal dipole-dipole forces • As a greater amount of energy is required to break stronger FoA, boiling pt of NH3 is higher
Trigonal Pyramidal Ex. - Charge Clouds - Bonds - Lone Pairs - Bond Angle - Hybridization -
NH3; 4; 3; 1; <109.5 degrees; sp^3
Bent (1 Lone Pair) Ex. - Charge Clouds - Bonds - Bond Angle - Hybridization -
NO2 -; 3; 2; <120 degrees; sp^2
which bond from each set is most ionic? Explain a. Al-O or Na-O b. K-Cl or Zn-Cl c. Fr-F or B-F
Na-O; K-Cl; Fr-F; Greater electronegativity difference between two atoms, the more ionic the bond
Ionic compounds in polar solvents
NaCl dissolves in water NaCl(s) —> Na+(aq) + Cl-(aq) • Ions drag a certain # of water molecules around with them in solution • smaller ions have stronger electric fields so they drag more water molecules around with them
which compound from each set is most ionic? Explain a. Al2O3 or NaCl b. KCl or FeO
NaCl; KCl; Greater the electronegativity difference between 2 atoms, the more ionic the bonds. the more ionic the bonds, the more ionic the compound
Shell models of 2 neutral atoms of Ne and Ar. Which atom would have higher 1st ionization energy? Justify
Ne -Ar has larger atomic radius than Ne, as it has an additional shell. -As radius of Ar is larger, its Ve- r held with a smaller force of attraction and requires less energy to remove them -According to Coulomb's Law, forces of attraction increases as distance between e-s and protons decreases.
Common Reductions in Acidic Solutions
Nitrate: NO3- —> NO Permanganate: MnO4- —> Mn 2+ Dichromate: Cr2O7 2- —> Cr 3+ Sulfite: SO3 2- —> SO4 2- Hydrogen Peroxide: H2O2 —> O2 • All the above oxidize p and d-block metals, sulfite ions, peroxides, and substances that have a lower (less positive) oxidation state than usual in acidic solutions
Will Mg oxidize Zn? Will Sn reduce Fe? Will Ag oxidize Fe? Will Ag oxidize Cu?
No, No, Yes, Yes
Argon, Ar, and Calcium cation, Ca^2+, r isoelectronic. Will they exhibit same photoelectron spectra? Justify
No, bc Ca^2+ has 20 protons in nucleus and Ar only has 18 protons in its nucleus. -According to Coulomb's Law, force of attraction on each of 18 e-s in Ca^2+ will be greater than force of attraction on each of e-s in Ar. For this reason, ionization energies for each ionization will be greater in Ca^2+. -Since both isoelectronic, 2 species will have same # of peaks, and peaks will show that they share same e- config.; however, peaks for Ca^2+ will have different energies than those for Ar due to having a lower effective nuclear charge
Does the photoelectron spectra (H, He, Li, Be) suggest a need to refine shell model of atom? Justify
No, bc these spectra support shell model. -The show that elements in 1st period of periodic table have one shell (n=1), and elements in 2nd period of period table have two shells (n=1 and n=2). -Shell model predicts that n=1 can hold up to two e-s and n=2 can hold up to 8 e-s. -Spectrum for Be shows that n=1 shell is holding 2 e-s and n=2 shell is holding 2 e-s.
Can prolonged exposure to highly intense infrared light cause e-s to be ejected from a clean metal surface? Explain
No, the frequency of infrared light is too low to eject e-s • To eject e-s from any metal surface a certain threshold frequency must be applied • Anything below that threshold frequency will not cause a single e- to eject, even if the metal is exposed to the light for several yrs
According to kinetic molecular theory, does a gas molecular move slower after it bounces off of the wall of a container? Explain
No, will continue to move at the same speed • KMT states that all collisions btwn gas particles and the walls of a container r elastic • No KE is lost in elastic collisions and if no KE is lost, then the velocity of the gas molecule must remain the same, as KE = 1/2 mv^2. • Molecule doesn't lose any mass during the collision, so it cannot lose any velocity if it retains the same amount of KE
Electronic Difference Ranges between Ionic, Polar Covalent, and Non-polar Covalent bonds
Non-polar Covalent Bond = 0-0.5 Polar Covalent Bond = 0.5-1.9 Ionic Bond = 1.9-3.5
Rank the following single bonds in order of increasing bond length: O-C, O-N, O-O, and O-F
O-F < O-O < O-N < O-C Bond length increase as the atomic radius of one or both of the bonding atoms increases
Explain why O2 is able to dissolve in water
O2 is non-polar and water is polar • When O2 dissolves in water, the polar molecules induce a dipole in the non-polar O molecules • Dipole-induced dipole FoA r able to hold a small concentration of O molecules in water
Solutions of sodium hydroxide and sulfuric acid are mixed. a. What is the strongest base in the reaction?
OH- + H+ → H2O OH- or NaOH
Ionization Energy: Every element has 1 extremely large increase in ionization energy.
Occurs when e- config. drops a principal quantum #, which causes radius to shrink much more than other ionizations
Is SF6 polar or non-polar?? Explain by discussing shape, polar bonds, and whether or not dipoles cancel
Octahedral so 6 S-F bonds and no lone pairs - polar individual bonds bc F is more electronegative than S - Non-polar overall compound bc dipoles cancel due to the symmetrical arrangement of the 6 S-F bonds
Forces of attraction between the electron and the nucleus result from ________________. The nucleus contains positively charged protons and neutral neutrons
Opposite charges
An ____________ is a graphic representation of the space that an electron will occupy 90% of the time.
Orbital
Collecting Gases over water
P(atm) = P(total) = P(gas) + P(water) • When measuring V of gas collected, must line up the water levels inside and outside the graduated cylinder • ensures that P inside cylinder is = to atmospheric pressure
Pressure Adjustment for Gases Under High Pressures (Low Volumes) (equation)
P(ideal) = P(measured) + (n^2 a)/(V^2) (Correction increases P(measured) to P(ideal) = P(measured) = P measured in the lab = P(ideal) = P expected when using the ideal gas equation = n = # of moles of gas = a = a constant for the specific gas in the system = V = V of the system (V(measured))
Combined Gas Law
P1V1/T1=P2V2/T2 • If P, V, or T changes, but number of moles remains the same, combined gas law equation can be derived from the ideal gas law equation in order to solve the problem • Must use absolute temperature (K)
Trigonal Bipyramidal Ex. - Charge Clouds - Bonds - Lone Pairs - Bond Angle - Hybridization -
PCl5; 5; 5; 0; 90 degrees and 120 degrees; sp^3d
Explain why standard enthalpy of vaporization, DeltaH(vap), values for each set of compounds below rn't the same b. PH3 and NH3
PH4 has LDF and dipole-dipole forces and NB3 has LDF and H-bonds • bc intermolecular FoA in these 2 substances r different, their enthalpies of vaporization will also be different
Ideal Gas Equation
PV=nRT P = pressure (atm) V= volume (L) n = number of moles R = (Molar Gas constant) 0.0821 L atm/K mol T = temperature (K)
Classify as a physical change, chemical change, or both. Justify by identifying the types of intermolecular or intramolecular forces that r involved in each processes and describing what happens to those forces while the processes r occurring. c) NH2F(L) —> NH2F(g)
Physical change • LDF and H-bonds in liquid NH2F r overcome, generating individual gaseous NH2F molecules
Classify as a physical change, chemical change, or both. Justify by identifying the types of intermolecular or intramolecular forces that r involved in each processes and describing what happens to those forces while the processes r occurring. f) H2O(s) —> H2O(L)
Physical change • LDF and H-bonds in solid water r stretched to produce liquid water
Classify as a physical change, chemical change, or both. Justify by identifying the types of intermolecular or intramolecular forces that r involved in each processes and describing what happens to those forces while the processes r occurring. a) CO2(s) —> CO2(g)
Physical change • LDF in solid CO2 r overcome, generating individual CO2 molecules
Pi or sigma bonds Which type of bond causes cis and trans isomers? Explain
Pi bonds cause the isomers bc they r rigid and prevent sigma bonds from spinning
Draw a V versus T graph, and plot the expected results of heating a gas from O K to 300 K at a constant P
Plot should consist of a straight line with a + slope that starts at the origin
Periodicity
Predictable physical and chemical trends that occur as one moves across a period or down a group in the periodic table. Ex. Atomic radii, Ionic radii, ionization energies, electron affinity, and electronegativity
Pressure (formula also)
Pressure (Pa) = Force (N) / Area (m^2) = Gasses exert P by bouncing off surfaces - Gas particles r evenly distributed in a container - The same number smash off every cm^2 per unit of time • Each collision exerts a force - The pressure is constant at constant temperatures (1 atm = 760 mm Hg = 760 torr)
Which if the following processes has the longer half-life? Justify Process Rate Law Rate Constant 1 Rate=k[A][B] k=6.79 M^-1 min^-1 2 Rate=k[A][B] k=14.55 M^-1 min^-1
Process 1 bc both 2nd order. has a slower rate when both processes share the same initial conc., as its rate constant has a smaller magnitude. Rate constant is inversely proportional to half-life
Overall Order for a Reaction
Rate = k [A]^m • [B]^n Overall Order of the Reaction = m + n
What is the difference btwn a reaction intermediate and a catalyst?
Reaction intermediate - substance that is produced in one elementary step and then consumed in another. It's not present before the reaction starts, nor is it present when the overall reaction is complete Catalyst - substance that lowers the activation energy of a reaction by providing an alternate mechanism through which the reaction can proceed. It's not produced or consumed by the chemical reaction. It's present before the reaction starts and regains its original form when the overall reaction is complete
Redox Reactions in Acidic Solutions (II)
Reactions btwn metals and Nitric Acid • NO3- will oxidize metals that H+ cannot
Boyle's Law
Relationship btwn P and V of gases V1P1 = V2P2 • V is inversely proportional to P
As a catalyzed reaction proceeds, does the net conc. of the catalyst increase, decrease, or remain the same? Explain
Remains the same • catalyst is added to the reaction system • It's consumed in one elementary step and regenerated in another
_______ ____ caused by shielding effect reduce the effective nuclear charge experienced by outer electrons
Repulsive forces
Seesaw Ex. - Charge Clouds - Bonds - Lone Pairs - Bond Angle - Hybridization -
SF4; 5; 4; 1; <90 and <120 degrees; sp^3d
Octahedral Ex. - Charge Clouds - Bonds - Lone Pairs - Bond Angle - Hybridization -
SF6; 6; 6; 0; 90 degrees; sp^3d^2
Isotope
Same atomic number, but different atomic masses. Same number of protons but not neutrons.
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces j. AsH3 and SbH3
SbH3, bc both LDF and dipole-dipole but SbH3 is larger and more polarizable than AsH3 • SbH3 experiences greater LDF • As a greater amount of energy is required to break stronger FoA, boiling pt of SbH3 is higher
Is XeO2F2 polar or non-polar?? Explain by discussing shape, polar bonds, and whether or not dipoles cancel
Seesaw so 2 F-O bonds and 2 lone pairs - Polar individual bonds bc F and O is more electronegative than Xe - Polar overall compound bc dipoles don't cancel
Spinning Single bond - Double bond -
Single - Sigma bonds r able to spin on an axis Double - Pi bonds prevent sigma bonds from spinning on this axis
For each pair of compounds listed below, identify the compound that has the highest boiling point. Justify ur choice in terms of intermolecular forces h. CH4 and SnH4
SnH4, bc both LDF but SnH4 is larger and has more e-s, making it more polarizable than CH4 • SnH4 experiences greater LDF • As a greater amount of energy is required to break stronger FoA, boiling pt of SnH4 is higher
Strong Bases
Soluble compounds containing the OH- Possible Cations: • All Group 1A Cations, Ca2+, Sr2+, or Ba2+
Is XeF4 polar or non-polar?? Explain by discussing shape, polar bonds, and whether or not dipoles cancel
Square planar so 4 Xe-F bonds and 2 lone pairs - polar individual bonds bc F is more electronegative than Xe - Non-polar overall compound bc dipoles cancel - Dipoles r = and opposite to one another in the same plane
HBr + H2O ---> H3O+ + Br- Weak or strong Acids and Conjugate Bases??
Strong acids/weak conjugate bases - H2O and Br- compete for protons - H2O stronger base, so wins most of the time and reaction goes to completion
Acid Strength
Strong acids experience ~ 100% ionization in water HA + H2O —> H3O+ + A- • 1 way arrow, as equilibrium lies far to the right Weak acids partially ionize in water HA + H2O <=> H3O+ + A- • 2 way arrow, as equilibrium lies to the left or ~ middle
Brass — A __________ Alloy
Substitutional • Zn atoms r substituted for some Cu atoms • Substitutional alloys remain malleable and ductile • Retains a "sea of e-" so it can conduct electricity • Density normally lies btwn those if component metals
A 1.0 mole pure sample of molten tin is dissolved in a 5.0 mole pure sample of molted copper. The solution is set aside to cool and solidifies. The atomic radius of tin is 140 pm and the atomic radius of copper is 128 pm a) Identify the type of alloy that is formed. Justify ur answer
Substitutional alloy is formed. Since atomic radii of the 2 elements r similar, tin will substitute for copper
Is BrF3 polar or non-polar?? Explain by discussing shape, polar bonds, and whether or not dipoles cancel
T-shaped so 3 Br-F bonds and 2 lone pairs - Polar individual bonds bc F is more electronegative than Br - Polar overall compound bc dipoles don't cancel due to asymmetrical arrangement of 3 B-F bonds
Is SO4 2- polar or non-polar?? Explain by discussing shape, polar bonds, and whether or not dipoles cancel
Tetrahedral so 4 S-O bonds and no lone pairs - polar individual bonds bc O is more electronegative than S - Non-polar overall compound bc dipoles cancel due to the symmetrical arrangement of the 4 S-O bonds
Surface Catalysis
The catalyst binds to or forms covalent bonds with a surface, thereby forming a new intermediate
Use the 'shielding effect' to explain why this e- has the lowest ionization energy
The e- in the n=4 shell is partially 'shielded' from the force of attraction by the inner core e- from the n=1, n=2, and n=3 shells. The e- in n=4 is repelled by the negative charges of those inner core e-, and this reduces the force of attraction between it and the positive nucleus.
Ion-Dipole
The forces of attraction between an ion and a polar molecule - smaller ion, condensed and attract more molecules to itself than larger ions
A 150.0 g pure sample of Ilmenite, FeTiO3, was analyzed and it was found to contain 36.81% Fe by mass. Would you expect this % to be the higher, lower, or the same in a 450.0 g pure sample of FeTiO3? Justify your answer.
The mass % of Fe would be the same (36.81%) in the 450.0 g pure sample of Ilmenite. Each compound in both samples contains exactly 1 Fe, 1 Ti, and 3 O. Average atomic mass of Fe would be the same in both samples as the ratio of the different isotopes of Fe would be the same in both samples, the average atomic mass of Ti would be the same in both samples as the ratio of the different isotopes of Ti would be the same in both samples, and the average atomic mass of O would be the same in both samples as the ratio of the different isotopes of O would be the same in both samples. For the reasons, the mass % of Fe would be the same in both samples.
Where is the lowest ionization energy in the shell model of Potassium located??
The outside electron of the 4th outer shell.
The reaction-energy profile diagram below outlines an uncatalyzed process Potential Energy ______________ / \ / \ l l / \ _________________/ \__________________ Reaction progress c) Explain why the presence of a catalyst increases the reaction rate.
The presence of a catalyst increases the reaction rate by providing an alternate mechanism for the reaction that has a lower activation energy. • When minimum collision energy that is required to trigger a chemical reaction is lower, a percentage of collisions btwn reactants will result in chemical reactions • If more collisions per period of time r resulting in chemical reaction, reaction rate is higher
Solute
The substance that is less plentiful in a solution
Solvent
The substance that is more plentiful in a solution
A 1.0 mole pure sample of molten tin is dissolved in a 5.0 mole pure sample of molted copper. The solution is set aside to cool and solidifies. The atomic radius of tin is 140 pm and the atomic radius of copper is 128 pm b) Identify the solvent in this solution. Justify
There r 5.0 moles of Cu and 1.0 moles of tin in the solution. Since Cu is more plentiful, it is the solvent
Do the peaks on infrared spectra point up or down? Justify
They point down, as % transmittance is in the y-axis • if the bind is absorbing most if the light, only a very small amount is transmitted through the sample
If given a metal and an ionic compound with the same metal in it...
This is also disproportionation, take the metal and the metal ion and form ions at the intermediate ox state. These often r left for an extended period of time as well
Is ammonia polar or non-polar?? Explain by discussing shape, polar bonds, and whether or not dipoles cancel
Trigonal Pyramidal so 3 N-O bonds and 1 lone pair - Polar individual bonds bc N is more electronegative than H - Polar overall compound bc dipoles don't cancel due to asymmetrical arrangement of 3 N-H bonds - N end is slightly - and H ends r slightly
Is PF5 polar or non-polar?? Explain by discussing shape, polar bonds, and whether or not dipoles cancel
Trigonal bipyramidal so 5 P-F bonds and no lone pairs - polar individual bonds bc F is more electronegative than P - Non-polar overall compound bc dipoles cancel due to the symmetrical arrangement of the 5 P-F bonds
Is BCl3 polar or non-polar?? Explain by discussing shape, polar bonds, and whether or not dipoles cancel
Trigonal planar so 3 B-Cl bonds and no lone pairs - polar individual bonds bc Cl is more electronegative than B - Non-polar overall compound bc dipoles cancel due to the symmetrical arrangement of the 3 B-Cl bonds
IE_He is almost ________ IE_H+ This increase can be explained through Coulomb's Law, as He has ______ as many protons as H
Twice
volume adjustment for gases under high pressure (equation)
V(ideal) = V(measured) - nb(Correction decreases V(measured) to V(ideal) = V(measured) = V of empty space + V of gas particles. (V measured in the lab) = V(ideal) = Corrected V, which can be used in the ideal gas equation. (V of actual empty space in the container = n = moles of gas = b = a constant for the type of gas
VSEPR Theory
Valence Shell Electron Pair Repulsion Theory - Charge clouds repel each other due to Coulombic forces - Terminal atoms move far away from one another as possible - Results in distinctive geometric shapes
Explain each of the following occurrences by referring to structure of atoms in question (energy levels, orbits, protons, etc.) -The atomic radius of Mg is smaller than the atomic radius of Ca.
Ve- in Mg r contained within 3s orbital and Ve- in Ca r contained within 4s orbital. -This means that outermost e-s in Ca experience greater shielding effect, possess more energy and r further from nucleus than outermost e-s in Mg. -According to Coulomb's Law, force of attraction decrease as distance between e-s and protons increases, so Mg has smaller atomic radius.
Explain each of the following occurrences by referring to structure of atoms in question (energy levels, orbits, protons, etc.) -Atomic radius of O is smaller than atomic radius of C
Ve-s of both elements r same shell (n=2). Thus, shielding effect experienced by outer e-s of both elements similar. -O atoms has 8 protons in nucleus while C atom only has 6 protons. -Addition of protons increases effective nuclear charge on Ve-s. -Moving from left to right, more protons r added. According to Coulomb's Law, increase in + charge increases force of attraction experienced by each e-, thereby decreasing radius. This gives O a smaller atomic radius.
Strengths of acids and bases (List)
Weak to strong Acid (CH4, H2O, NH4+, HF, HNO3, HCl) Base (Cl-, NO3-, F-, NH3, OH-, CH3-)
Determining Rate Law • Slow initial step
When the mechanism has a slow initial step, the rate law for the overall reaction is = to the rate law for the 1st step
The energy profile diagram below was plotted for the following second order elementary reaction: A + BC <-> AB + C Potential Energy ______________ / \ / \ l l / \ _________________/ \__________________ b) At high temperatures a relatively large fraction of collisions btwn reactants resulted in the formation of products. Describe the interactions btwn the reactants from the moment of a collision through to the formation of separate products
When 2 molecules collide, KE from their motion is converted into PE • This PE cultivates itself in the bonds btwn all of the reacting atoms (A + BC —> A-B-C) • In this case, A forms a new bond with B, and the bond btwn B and C lengthens • At the top of the curve, PE contained within the bonds of A-B-C has reached a maximum • At this pt, we don't have reactants or products • What we have is an extremely unstable aggregation of all of the atoms contained by the reacting molecules • During the downward section of the graph, PE begins to drop • Electron density btwn A and B, causing that bond to shorten • Electron density btwn B and C decr., causing that bond to start stretching • When the graph plateaus again, there r 2 separate species: AB and C
The table below outlines the results from 3 experiments, which were conducted at the same temperature, involving the following reaction Ex: [O2]initial [NO]initial Initial Reaction Rate 1 0.022 0.026 0.0256 M/s 2 0.022 0.013 0.0064 M/s 3 0.044 0.013 0.0128 M/s a) The results show that the initial rate increased when the initial conc. of either reactant increased. Explain why increasing the conc. or partial pressure of a reactant can increase the rate at which the reaction proceeds
When the conc. of a reactant incr., there is more of that reactant circulating within the same volume. • As a result, there will be more collisions btwn reactants per second • Reaction rate incr. when collision rate incr.
Linear Ex. - Charge Clouds - Bonds - Lone Pairs - Bond Angle - Hybridization -
XeF2; 5; 2; 3; 180 degrees; sp^3d
Square Planar Ex. - Charge Clouds - Bonds - Lone Pairs - Bond Angle - Hybridization -
XeF4; 6; 4; 2; 90 degrees; sp^3d^2
Does the photoelectron spectra (C, N, O, F, Ne) suggest a need to refine shell model of atom? If so, is there another model that provides a better explanation of this data? Justify
Yes, bc these spectra do no support shell model. -show that elements in 2nd period of periodic table have 1 shell in n=1, and 2 subshells in n=2 that r at different energy levels. 1st subshell in n=2 can hold up to 2 e-s and 2nd subshell in n=2 can hold up to 6 e-s. -Quantum mechanical (QM) model used to explain why 2 subshells in n=2 shell. -According to QM model, n=2 contains 2s orbitals, which can hold up to 2 e-s at same quantized energy level, and 3 2p orbitals, each of which can hold 2 e-s. All e-s in 2p r at same quantized energy level.
After learning about PES data, do you see a need to refine the Shell Model of an atom?
Yes, shell model states that all e- within given shell are at same energy level. PES data shows that there are 2 subshells in n=2 and 3 subshells in n=3
effective nuclear charge (Zeff)
Zeff = z - σ Zeff - charge experienced by an e- Z - actual nuclear charge (atomic number of element) σ - shielding constant (0 < σ < Z)
Reaction Orders (m and n) Zero, First, and Second Order Reactions
Zero • Doubling the concentration of that species, has no affect on the reaction rate First • Doubling the concentration of that species, doubles the reaction rate Second • Doubling the concentration of that species, quadruples the reaction rate
Zinc metal is placed into a solution of hydrochloric acid. a. What substance is reduced in the reaction?
Zn + 2H+ → Zn2+ + H2 H+
How would a straight ln[A] line change in the presence of a catalyst?
[A] and ln[A] decrease at a faster rate in the presence of a catalyst • Initial conc. of A is the same in both situations
Zeroth Order Integrated Rate Law
[A]t = -kt + [A]0 [A]0= initial conc (at t=0s) [A]t= conc after some period of time • A plot of [A]t (conc.) vs t (time) produces a straight line for 0th order reactions, as the rate does not change when conc changes • This is used to determine if a reaction is 0th order, as a straight line will only occur if reaction is 0th order Slope = -k
Combustion Analysis
a method of obtaining empirical formulas for unknown compounds, especially those containing carbon and hydrogen, by burning a sample of the compound in pure oxygen and analyzing the products of the combustion reaction
sigma bond
a single covalent bond that is formed when an electron pair is shared by the direct overlap of bonding orbitals - 1st bond between 2 atoms (hybridized orbital) - contain more energy as the overlap between the orbitals is stronger
A two step reaction is outlined below. H2O2 + I- —> H2O + IO- (slow step) H2O2 + IO- —> H2O + O2 + I- (fast step) a) overall reaction?? b) Identify intermediate in this reaction mechanism c) Rate law for each of the elementary steps?? d) Rate law for the overall reaction??
a) 2H2O —> 2H2O + O2 b) IO- bc it's produced and consumed in the reaction c) Step 1. Rate = k1 [H2O2][I-] Step 2. Rate = k2 [H2O2][IO-] d) Rate = k [H2O2][I-]
A two step mechanism is outlined below 2NO —> N2O2 (fast equilibrium) N2O2 + Br2 —> 2NOBr (slow) a) overall reaction?? b) Identify the intermediate in this reaction mechanism. Justify c) Rate law for the overall reaction?? d) Order of the reaction with respect to NO according to the above mechanism? Justify
a) 2NO + Br2 —> 2NOBr b) N2O2 bc it's produced and consumed in the reaction c) k1 [NO]^2 = K-1 [N2O2] [N2O2] = K1/K-1 [NO]^2 Rate = k2 [N2O2][Br2] Rate = K2 (k1/k-1 [NO]^2) [Br2] Rate = k3 [NO]^2 [Br2] d) reaction id 2nd order with respect to NO, as the [NO] is raised to the power of 2 in the rate law
A two step mechanism is outlined below. NO2Cl —> NO2 + Cl (slow step) NO2Cl + Cl —> NO2 + Cl2 (fast step) a) overall reaction?? b) Identify intermediate in this reaction mechanism. Justify c) Rate law for each of the elementary steps?? d) rate law for overall reaction??
a) 2NO2Cl —> 2NO2 + Cl2 b) Cl bc it's produced and consumed in the reaction c) Step 1. Rate = k1 [NO2Cl] Step 2. Rate = k2 [NO2Cl][Cl] d) Rate = k2 [NO2Cl]
Location highest on these trends... a) Atomic radius b) Ionic radius c) Ionization energies d) Electron affinity e) Electronegativity
a) Atomic radius - Bottom left (Fr) b) Ionic radius - Bottom left (Fr) c) Ionization energies - Top right (He) d) Electron affinity - Top right minus Noble gases, N, and Alkali Earth Metals (F) e) Electronegativity - Top right minus Noble gases (F)
A two step mechanism is outlined below. F2 + NO2 —> NO2F + F (slow step) NO2 + F —> NO2F (fast step) a) overall reaction?? b) Identify intermediate in this reaction mechanism. Justify c) Rate law for each of the elementary steps?? d) rate law for overall reaction??
a) F2 + 2NO2 —> 2NO2F b) F bc it's produced and consumed in the reaction c) Step 1. Rate = k1 [F2][NO2] Step 2. Rate = k2 [F][NO2] d) Rate = k [F2][NO2]
a) Which color of light has the highest frequency: red or green?? b) Which color of light has the longest wavelength: green or violet?
a) Green: shorter wavelength = higher frequency b) green
Ionic Compounds of Mg^2+ a) Write the ionic formula for every compound that can be formed between Mg and an element from Group 7A. b) Provide an explanation for ratio of bonding for the compounds of Mg^2+ in part (a) c) Will ratio of cation to anion be the same or different for when other Group 2A cations form ionic compounds with anions of Group 7A? Justify
a) MgF_2, MgCl_2, MgBr_2, MgI_2, MgAt_2 b) 1:2, bc Mg has 2+ and all 7A have 1- c) Same, bc all Group 2A cations have a charge of 2+ and all Group 7A anions have a charge of 1- so in order to be a neutral atom, the ratio will be the same.
The rate law for the overall reaction outlined below is: Rate = k [NO][Cl2]. NO + Cl2 —> NOCl2 NOCl2 + NO —> 2NOCl === 2NO + Cl2 —> 2NOCl a) Identify the intermediate in this reaction mechanism. Justify b) Which step occurs the fastest? c) Which step determines the overall rate of the reaction??
a) NOCl2 bc it's produced and consumed in the reaction b) Step 2. NOCl2 + NO —> 2NOCl bc it doesn't determine the rate of the overall reaction. Rate law for the overall reaction is the same as the rate law for the 1st step, which means that the first step is the slow, rate determining step c) Step 1. NO + Cl2 —> NOCl2 determines the overall reaction. The rate law of the overall reaction is: Rate = k [NO][Cl2]. This is also rate law for this step. Step 1 is the slow step, which determines the rate of the overall reaction
Reaction below was found to be second order for A and zero order for B A + B —> C + D Following mechanism was proposed for this reaction Step 1) 2A —> C + E (slow step) Step 2) B + E —> A + D (fast step) a) Rate law for this reaction?? b) Give 2 reasons why the above mechanism is possible
a) Rate = k [A]^2 b) 1. When the 2 reactions r added together, we get A + B —> C + D, which is the same as the overall reaction 2. Slow step is consistent with the rate law, as B is zero order and thus is not included in the rate law; and A is 2nd order and raised to the power of 2 in the rate law, which means that 2 A particles collide in the rate determining step
H-atoms can absorb and emit photons containing 4.8x10^-19 J of energy a. If a H atom absorbs a photon containing 4.8x10^-19 J of energy, what component of the atom experienced an increase in energy? c. If a H atom emits a photon containing 4.8x10^-19 J of energy, what component of the atom experienced a decrease in energy?
a) an e- absorbed the photon and experienced an increase in energy c) An e- emits the photon and experienced a decrease in energy
Percent Yield
actual yield/theoretical yield x 100
aminopropane, CH3CHNH2CH3, and isobutane, C4H10 • Explain why aminopropaneis soluble in water, whereas isobutane isn't soluble in water
aminopropane polar and capable of forming H-bonds with water • Isobutane is non-polar and can't form H-bonds • aminopropane dissolve in water bc strong H-bonds (or d^2 FoA) that form with water molecules • No strong intermolecular FoA exist btwn isobutane and water
H-atoms can absorb and emit photons containing 4.8x10^-19 J of energy b. What can be said about the difference in energy btwn 2 of the sublevels in a H atom. Justify
b) Difference in energy btwn 2 of the sublevels in a H atom must be 4.8x10^-19 J • For a photon to absorb and e-, it must contain the exact amount of energy required to move that e- from a lower energy level to a higher energy level • Furthermore, when an e- drops from a higher energy level to a lower energy level, ot emits a photon that is = to the difference in energy levels • As H atoms can absorb and emit photons containing 4.8x10^-19 J of energy, this must he the difference in energy btwn 2 of its sublevels
Classify as a physical change, chemical change, or both. Justify by identifying the types of intermolecular or intramolecular forces that r involved in each processes and describing what happens to those forces while the processes r occurring. d) NaCl(s) —> Na+(aq) + Cl-(aq)
both bc dissolving an ionic compound in water can be classified as a physical change and a chemical change • Ionic bonds r broken (chemical change) and ion-dipole intermolecular forces btwn water and the ions r formed (physical change)
Speed of light formula
c=λv Speed of light (3x10^8 m/s) = λ (wavelength (m)) v (Frequency (s^-1 or Hz))
Classify as a physical change, chemical change, or both. Justify by identifying the types of intermolecular or intramolecular forces that r involved in each processes and describing what happens to those forces while the processes r occurring. e) NH2F(L) —> 1/2 N2(g) + H2(g) + 1/2 F2(g)
chemical change • covalent bonds in the NH2F molecule r broken and new covalent bonds r formed
If given a metal or nonmetal (including diatomics — usually "bubbled through") and the soluble ionic compound...
cross out the always soluble ion and replace the respective metal or nonmetal ion from the compound. Single replacement reaction
When completing a ground state electron configuration for Zn^2+.
d-block cations lose their electrons from the highest energy s-orbitals before they start losing them from the highest energy d-orbitals.
Although the average distance between the nucleus and electrons _________ as subsequent subshells are added within a shell, the ionization energy ________ due to an __________ in the shielding effect.
decreases; decreases; increases
Electronegativity and Bond Polarity
difference in electronegativity large = POLAR (or ionic, if very large difference) electrons shared equally (electronegative values are equal) = nonpolar covalent
Ethanol _____ form H-bonds
does not - H bonded to C - H needs to bond with F, O, or N to form an H-bond
Representative Particles of element covalent compound ionic compound
element --> atom covalent compound --> molecule ionic compound --> Formula unit
Exothermic reaction vs Endothermic Reaction
exo = Bonds in products contain less PE than bonds in reactants endo = Bonds in products contain more PE than bonds in reactants • Delta E is the energy lost of gained in a reaction
intermolecular forces
forces of attraction between molecules (can be individual particles)
pi bonds
forms when parallel orbitals overlap and share electrons. - unhybridized p-orbitals and occur in double or triple bonds (weaker)
Do non-metals gain or lose electrons in order to acquire a full octet?
gain and in doing so, they form - ions
Electron Affinity: Energy change that occurs when an electron is added to a ________ atom to form a negative ion. It is a measure of how much an element want to __________ another e-.
gaseous; accept
Although the average distance between the nucleus and an electron in 2s is ________ than that of an electron in 2p, electrons in 2s spend some of their time much closer to the nucleus than those in 2p. As a result, electrons in 2p experience a ______ shielding effect. These _____ repulsive forces that the 2p electrons experience from the 1s electrons result in a lower ionization energy for the 2p electrons.
greater
Strong FoA —> ____ boiling point —> _____ energy needed
higher; more
as Atomic radii increases, bond length ________, PE _____ and Bond energy __________
increases, increases, decreases
Mass Spectrometry
is an analytical technique that measures the mass-to-charge ratio of ions. The results are typically presented as a mass spectrum, a plot of intensity as a function of the mass-to-charge ratio. It is used to compare the masses of isotopes.
Mole
is the fundamental unit for counting particles on the macroscopic level
If given two soluble ionic compounds...
it is a double replacement. So, cross out the always soluble ions and write the net ionic to form the precipitate
If given a hydrocarbon and O2...
it is combustion and will produce CO2 and H2O
If given a metal and told it burns in the air (read reacts with oxygen)...
it will form a metal oxide
If given a nonmetal and told it burns in air (read reacts with oxygen)...
it will form a nonmetal oxide
The Arrhenius Equation
k=Ae^(-Ea/RT) k= rate constant E(a) = Activation energy (J) R = 8.314 J/mol•K T = absolute temperature (K) A = A constant related to the frequency of collisions and the probability that the orientation could produce a reaction • The Arrhenius Equation shows that increasing the temperature increases the rate of a reaction — As the temperature increases, -E/RT becomes less negative and the rate constant, k, increases — As the rate constant, k, increases, the rate increases rate = k rate = k[A] rate = k [A]^2
Coulomb's Law F=
kq1q2/r^2 F = Force of attraction k = Constant q = Magnitude of charge associated with a particle - protons or electrons d = Distance between charged particles
If given an acid and base where one is strong and one is weak...
leave the weak together and take the acidic or basic part of the strong and react to neutralize
These elements _______ electrons from their highest s-sublevel first before losing from their d-sublevel
lose
Do metals gain or lose electrons in order to acquire a full octet?
lose and in doing so, they form + ions
Electrons are added to the ________ energy orbital available. This is because nature always favors _________ energy systems. Luckily, there is a format that can be followed to determine the _______energy available
lowest; lower; lowest
Incomplete Octets
molecules or ions with fewer than eight electrons around an atom
In general, the more effectively the electrons within a subshell are able to ______ ____ _________ _______, the __________ the ionization energy of those electrons
penetrate the shielding electrons; greater
Ethanol, C2H4O, and methanol, CH3OH • Identify the types of intermolecular forces that exist in a pure sample of ethanol • and Methanol
pure ethanol has LDF & dipole-dipole forces. • dipole-dipole forces occur, as the structure is slightly polar. • electronegative O will acquire a partial - charge and that each atom bonded to the same C will acquire a partial + charge = LDF and H-bonds
Electron Affinity: =If value is -, it _______ energy (___________) -The more - the more it want to ________ e- =If value is +, it _______ energy (___________) -It _______ want to accept the e-
releases; exothermic; accept requires; endothermic; does not
2nd ionization energy
same as first ionization energy, except the alkali metals are the highest; this is because once group 1A loses one electron, it has an octet, and it takes the most energy to pull an electron from a full last energy level
Electrons in __________ ____ spend more of their time further away from the nucleus. Electrons in outer shells are partly "_________" from forces of attraction by inner core electrons. This ________ ________ (repulsion from inner electrons) reduces electrostatic attractions between the outer electrons and the nucleus.
successive shells; shielded; shielding effect
Electron Affinity
the energy change that occurs when an electron is added to a gaseous atom to form a negative ion
If given nitric acid and a metal...
the metal will lose e-s to the nitrate ion. (See stuff sheet) Non-trivial redox
Bond Order (Def and equation) When the bond order increases... = Bond length _______ = PE associated with the bond _______ = bond energy ________
the number of bonds between two atoms (Bonds total / Bond sites) decreases, decreases, increases
Heat of fusion (triangleHfus)
triangleHfus - the heat absorbed as 1 mole of a solid liquifies = Energy is required ti expand/sever the intermolecular FoA, as a molecule moves from the solid to the liquid phase = This is why molar heat of fusion, triangleHfus values r always + = Melting is always an endothermic process
Heat of Vaporization (triangleHvap)
triangleHvap - heat absorbed as 1 mole of a liquid becomes gaseous = energy is required to sever the intermolecular FoA, as a molecule moves from the liquid to the gas phase = Vaporization is always endothermic, so triangleHvap values r + = Ideally, there r no intermolecular FoA btwn gas particles
NH+ + H2O <---> H3O+ + NH3 Weak or strong Acids and Conjugate Bases??
weak acids/strong conjugate bases - H2O and NH3 compete for protons - NH3 stronger base, so wins most of the time and reaction lies to the left
Which of the following are isoelectronic? a) Ne and F- b) Ca^2+ and Se^2- c) N and F- d) I- and Ba^2+ e) K+ and Ca^2+
yes, no, no, yes, yes
The Structure of NaCl
— Each Na cation in surrounded by 6 Cl anions — Each Cl anion is surrounded by 6 Na cations - Arrangement of ions maximizes the Coulombic forces of attraction between cations and anions and minimizes repulsive forces between ions with like charges
C2H4 reacts with O2 to form CO2 and water b) Explain why all atoms were conserved during this reaction
• 1 C2H4 molecule reacted with 3 O2 molecules to form 2 CO2 molecules and 2 H2O molecules • Reactant side of the equation has 2 C atoms and the product side of the equation has 2 C atoms • Reactant side of the equation has 4 H atoms and the product side of the equation has 4 H atoms • Reactant side of the equation has 6 O atoms and the product side of the equation has 6 O atoms • Atoms formed new molecules, but they were all conserved
Standard Temperature and Pressure (STP) for Gases is 0*C and 1 atm
• 1 mole of any gas particles will occupy 22.4 L of space at STP
Einstein's Theory (1905)
• A beam of light is a stream of particles called photons • Energy of a photon is related to its frequency according to E=hv • Quantum of Planck is a particle - a photon • If the frequency of a photon is below a certain threshold, no e-s r ejected • If the frequency of the photon is at or above a certain threshold, its energy is transferred to the e- - This causes the e- to overcome the FoA holding it to the metal - E- absorbs the photon
Lowering the T of a system causes deviations from the ideal gas law. Explain
• 2 factors that cause deviations from ideal behavior r an increase in attractive forces btwn particles and a reduction in free space relative to the V of the container • At low T, gas particles move slower and r closer together • FoA exist btwn gas particles when they r in close proximity to one another and these attractive forces reduces reduce the expected pressure exerted by the gas • Ideal gas law assumes that gas particles have no V of their own, as their V is negligible when compared to the overall V of the container • When the V occupied by the particles makes up a relatively high percentage of the total V inside the container, the gad doesn't behave ideally
Ion-Dipole vs. Ionic Bonds
• 2 forces work against one another through Coulomb's law • 1 of forces will be stronger than the other • Mg(OH)2 isn't soluble in water and Ba(OH)2 is, bc, for alkaline earth metal hydroxides, FoA from ionic bonds decrease more rapidly that the ion-dipole intermolecular forces when moving down the group
Use Coulomb's law and visual representations to explain why BaSO4 is not soluble in water and why MgSO4 is soluble in water
• 2 opposing forces to consider when examining the solubility of an ionic compound in water. There r ion-dipole forces btwn the water molecules and the ions, which r trying to dissolve the compound; and there r ionic bonds btwn the anions and cations, which r trying to hold the solid structure together • Ion-dipole forces btwn water and Mg 2+ r greater than the ion-dipole forces btwn water and Ba 2+. This is bc Mg 2+ has a smaller ionic radius, so there is a shorter distance it and - ends of the water molecules • This can also be explained through Coulomb's Law, F=k (Q1Q2)/d^2 • Ion-dipole forces btwn Mg 2+ and water and SO4 2- and water r stronger than the ionic bonds btwn Mg 2+ and SO4 2-. This explains why MgSO4 is soluble • Ion-dipole forces btwn Ba 2+ and water and SO4 2- and water r stronger than the ionic bonds btwn Ba 2+ and SO4 2-. This explains why BaSO4 is soluble
Catalysis
• A catalyst increases the rate of a chemical reactions by providing a new and more efficient mechanism • The new mechanism will have: — a lower activation energy, and/or — a higher frequency of collisions with an orientation that could produce a reaction • Catalysts r added to the system — They r there before the reaction starts and they return when the reaction is complete — Bc of this, the new conc. of the catalyst remains constant • A catalyst provides a mechanism with a lower activation energy, thereby increasing the reaction rate • A catalyst lowers the activation energy for the forward and the reverse reactions — K(eq) for a reaction is the same at the same temperature, with of without the catalyst
Spectroscopy
• A method of analysis which is based upon the absorbance of electromagnetic radiation by matter • Used to acquire data pertaining to the structure of a molecule or the concentration of a species I(O) = I(T) + I(A) I(O) - Intensity of electromagnetic radiation striking sample I(T) - Intensity of electromagnetic radiation exiting sample I(A) - Intensity of electromagnetic radiation absorbed by the sample
Reaction Mechanisms • Reaction Intermediate
• A substance that is produced and then consumed during the overall reaction
Arrehenius Acids and Bases
• Acids dissociate in water to produce H+ ions HA —> H+ + A- • Bases dissociate in water to produce OH- ions BOH —> OH- + B+
Collision Rate increase...
• As the conc. of reactants in the liquid or gas phase increases • As the surface area of reactants in the solid phase increases • As temperature increases Not every collision triggers a chemical reaction
Is the actual V of a gaseous system less than, equal to, or greater than the V that would be predicted using the ideal gas law equation. Explain.
• Actual V of a gaseous system is less than the V that would be predicted using the ideal gas law equation • Ideal gas law assumes that the gas particles in a system don't occupy any V; however, gas particles do occupy a V and that V must be taken into consideration under conditions of high P and low T • Actual V of a gaseous system is the V of the container minus the V occupied by the gad particles
Combustion reactions
• All combustion reactions r redox reactions • Products for combustion of any hydrocarbon r always CO2 and H2O • O2 is required reactant in all combustion reactions • 2 C2H2 + 5 O2 —> 4 CO2 + 2 H2O
Infrared (IR) Spectroscopy
• All covalent bonds in molecules r vibrating • Bond length is the average distance btwn nuclei • Covalent bonds have a vibrational frequency that is in the IR region of the electromagnetic spectrum • IR radiation of exactly the same frequency will be absorbed by the molecule • Vibrational frequencies depend on the mass of the atoms and the strength of the bonds • Frequency is related to wavelength - c=(Wavelength) • v = IR spectra can used to identify bond types, functional groups, and compounds • Molecules the share the same functional group, such as alcohols or carboxylic acids can be identified through IR spectroscopy, as they will have absorption peaks within the same range • Every compound has a characteristic IR spectrum that it can be identified through
C2H4 reacts with O2 to form CO2 and water c) explain how the law of conservation of mass applies to this reaction
• All the atoms that were contained in the reactant molecules r present in the product molecules • No atoms were lost and no atoms were gained in this reactions • mass of these atoms is constant, so no mass was lost or gained in the chemical reaction
Ultraviolet/Visual (UV/Vis) spectroscopy
• An absorption spectrometer is used to measure the absorbance of a sample at wavelengths btwn about 200 nm and 800 nm • The peaks represent wavelengths that correspond to the energy associated with possible electronic transitions within the molecule • The following e- transitions r possible with UV and visual light btwn 200 nm and 800 nm - transitions r only possible when the compound has at least 1 LP. LP r common on O, N, and halogens - Transition is only possible of the compound has pi-bonds, which r present in double and triple bonds - Energy contained by the incident photons must be exactly the same as the difference in energy btwn the 2 MOs in order for the photons to be absorbed - In this molecule, 3 different frequencies of light would cause e- transitions • Colorless species can only absorb UV light btwn about 200 nm and 400 nm in these experiments - The peak occurs in the UV range of the electromagnetic spectrum, as CH2=CH-CH=CH2 is colorless - CH2=CH-CH=CH2 has no LP, so the e- transitions occurred at the pi-bond portions of the double bonds • Following e- transitions r possible with UV and visual light btwn 200 nm and 800 nm - Energy contained by the incident photons must be exactly the same as the difference in energy btwn the 2 MOs in order for the photons to be absorbed - In this molecule, 3 different frequencies of light would cause e- transitions • Colorless species can only absorb UV light btwn about 200 nm and 400 nm in these experiments - Peak occurs in the UV range of the electromagnetic spectrum, as CH2=CH-CH=CH2 is colorless - CH2=CH-CH=CH2 has no LP, so the e- transitions occurred at the pi-bond portions of the double bonds • Colored species will always absorb light from visual spectrum, but could also absorb UV light in these experiments - 2 peaks occur in the visual spectrum—> Oxygenated hemoglobin is bright red - Hemoglobin's structure contains several pi-bonds and LP
A container is filled with Ar gas at -48'C and sealed. After sitting on a lab bench at room temperature for several minutes, the lid blows off and the gas escapes. Explain why this happened
• Ar gas was at a very low T when the container is sealed and when gases r at a low T, the particles/atoms r relatively close to one another • As heat from the room flows into the container, gaseous Ar atoms started moving faster • P inside the container became overpowered the strength if the seal • When the seal broke, gas expanded and when the T of a gaseous system increases, P and/or V must also increase
Why do we have different colors of light?
• As wavelength/frequency changes, color changes • But there is a duality to light - Behaves like a wave, and - Behaves like a particle (a photon) • As wavelength/frequency changes, the energy per photon changes E=hv
Molar Mass, Molecular Speed, and Temperature
• At any given temperature, average KE of all gas particles is the same • Gases with smaller molar masses will have higher average velocities • Gases with larger molar masses will have lower average velocities KE = 1/2 mv^2
Maxwell-Boltzmann distribution
• At higher temperatures, a larger percentage of particles will be able to convert their KE in into the PE needed to overcome the E(a)
Collision Energy and Temperature
• At higher temperatures, more reactants collide with enough energy to cause a reaction
Hybrid Orbital Theory
• Atomic orbitals on the same atom combine in order to form hybrids • Atomic orbitals on different atoms overlap in order to form covalent bonds • Each atom in the compound retains its associated orbitals and e-s • This theory correlates with observed bond angles in molecules
A gaseous system is kept at 25.0'C. A chemist slowly increase the temperature of the system until it reaches 50.0'C. Did the average KE of the gas particles in the system double when he did this. Justify
• Average KE of the gaseous particles in the system increases, but it didn't double • Average KE of the particles in a system is proportional to the Kelvin temperature scale (absolute T) • If the T in Kelvin doubled, the average KE would have double but it didn't occur • 25.0 + 273 = 298 K 50.0 + 273 = 323K 2x298 K doesn't = 323 K
Suppose u have 2 identical 1.0 L sealed containers. Both containers r kept at exactly 25'C. One vessel contains only Ne gas at 1.5 atm, and the other contains only Xe gas at 2.5 atm a. Is the average KE possessed by the Ne atoms greater than, equal to, or less than that of the Xe atoms? Explain
• Average KE possessed by the Ne atoms is = to that of the Xe atoms • T is a measure of the average KE of the particles in a system • = T means that the average KE is also =
Explain why standard enthalpy of vaporization, DeltaH(vap), values for each set of compounds below rn't the same d. BH3 and OF2
• BH3 has LDF and OF2 has LDF and d^2 forces • bc intermolecular FoA in these 2 substances r different, their enthalpies of vaporization will also be different
Basic solutions Common Reduction in Basic Solutions
• Basic solutions have a higher concentration of OH- • Add same # of OH- to Eliminate however many H+ • Permanganate: MnO4- —> MnO2 • Permanganate will oxidize p and d-block metals, sulfite ions, and substances that have a lower (less +) oxidation state than usual in basic solutions
A real gas will behave more like an ideal gas when the pressure of a system decreases and the temperature remains the same. Explain
• Bc average distance btwn gaseous particles increases as the P decreases and when the gas particles further apart, attractive forces btwn particles r greatly reduced • This causes gas particles to behave as though they have no interaction with 1 another aside from elastic collisions • Thus, there is no reduction in the expected P due to FoA btwn particles
Fractional distillation was used to isolate an unknown volatile substances that had contaminated the well water at a rural property a. Is the boiling pt of the unknown substance greater than, less than, or equal to 100'C at 1.0 atm? Justify
• Boiling pt of the unknown substance is less than 100'C at 1.0 atm • Vapor pressure of the unknown substance when it's in the liquid phase must be greater than that of water at any given T in order for it to be isolated through fractional distillation • As a substance boils when its vapor P = atmospheric P, boiling pt of the unknown substance must be less than 100'C at 1.0 atm
Explain why CH3OH is miscible in water whereas CH3(CH2)6OH is not
• Both CH3OH and CH3(CH2)6OH can form H-bonds with water - CH3OH had a shorter non-polar component around the C atoms, so most significant intermolecular force possessed by each compound is H-bonds - Bc both share the same type of intermolecular forces, they r very soluble in one another • CH3(CH2)6OH has a large non-polar C chain, which is 7 C long - Water molecules have a greater attraction for one another (due to their strong H-bonds) than they do for long hydrocarbon chains, which can only offer weak dipole induced dipole and LDF. - Solubility of alcohols decreases drastically as C r added
A. Full saturated fatty acid B. double bonded at 1 part unsaturated fatty acid • most likely to be a solid at room temperatures
• Both about same size and have same # of e-s (b has 2 fewer e-s that a, but b has pi-bond which increases polarizability) • Both can form H-bonds at the end w/ the OH- group but LDF will be stronger in a due to its shape • a more likely bc it is saturated which means linear structure overall • bc linear stack up well, many pts of contact btwn neighboring molecules, which means more locations where LDF can be established • B is unsaturated as it has a double bond btwn 2 C in C chain which causes overall structure to bend at that pt • bc of kink, molecules don't stack up well, so fewer pts of contact btwn neighboring molecules which means fewer locations where LDF can be established
Which of the compounds below is most soluble in water? Justify. HOCH2CH2OH or CH3CH2OH
• Both compounds have non-polar C chains that r the same length • HOCH2CH2OH is most soluble in water, bc both ends of the molecule can form H-bonds with water, whereas only one end of CH3CH2OH can form H-bonds with water
Explain why standard enthalpy of vaporization, DeltaH(vap), values for each set of compounds below rn't the same c. C2H6 and C3H8
• Both only experience LDF but bc C3H8 is larger and has more e-s, it is more polarizable and this has larger dispersion forces • bc intermolecular FoA in these 2 substances r different, their enthalpies of vaporization will also be different
Suppose u have 2 identical 1.0 L sealed containers. Both containers r kept at exactly 25'C. One vessel contains only Ne gas at 1.5 atm, and the other contains only Xe gas at 2.5 atm C. Does the vessel with the Xe gas contains more, fewer, or the same # of gas particles as the vessel of Ne gas? Explain
• Both vessels r 1.0 L and 25'C and the P in the vessel with the Xe gas is higher, so there must be more moles of gas in that container • When there r more moles of gas occupying the same V, when both systems r at the same T, there will be more collisions per unit of time with the walls of the container, and therefore, the P will be higher
Is the dissolving of Al(NO3)3 in water a chemical process, a physical process, or both? Justify
• Both, bc chemical processes involve the breaking and/or formation of chemical bonds • Ionic bonds btwn Al 3+ and NO3 - r broken during the dissolving process • Physical process involve changes in intermolecular forces • Ion-dipole intermolecular forces r established during the dissolving of Al(NO3)3
A piece of paper catches on fire and burns. Has a chemical change occurred or has a physical change occurred? Justify
• Chemical change has occurred • Production of heat and light r indications of chemical changes
Two solutions r at 25*C r mixed. The temperature of the combined solution increases to 32*C and a white precipitate forms. Has a chemical change occurred or has a physical change occurred? Justify
• Chemical change occurred • Changes in temperature and formation of precipitates r indications of chemical changes
Chromatography and Solubility
• Chromatography paper is composed of non-polar C chains with -OH groups that can form H-bonds • Max height traveled by the mainly non-polar solvent • Solution: Mainly non-polar solvent, solute A, and solute B • Stationary phase is chromatography paper, and mobile phase is solvent used • As solvent moves up the piece of paper it carries solute particles with it • Distances that the different solute travel up the paper depend on their relative attractions for the moving solvent and the stationary paper • Solute particles that can form H-bonds at several locations along their structures will not travel very far up the paper, as the molecules in the paper contain many -OH groups - These solute particles form H-bonds with paper relatively close to the solutions surface • Solute particles that r mostly non-polar will have weak attractions for the paper and relatively strong attractions for the mainly non-polar solvent - These particles will be deposited further up the paper
What r the main factors that account for the extreme hardness of diamond?
• Diamond is a network solid, meaning that each diamond is one massive molecule held together with covalent bonds • All C r bound together with sp^3 hybrid orbitals • Means that there is a tetrahedral geometry around each C atom, which is a very strong configuration
Why do FoA btwn gas particles increase when they r closer together?
• Distance is in the denominator of the Coulomb's Law equation. • As distance btwn particles decreases the intermolecular FoA btwn the particles will increase
Disproportionation Reactions (I)
• Element in one oxidation state simultaneously undergoes both oxidation and reduction • Element must, therefore, have at least 3 oxidation states, and it must be in an intermediate state
Activity Series
• Elements that r less easily oxidized, will oxidize elements that r more easily oxidized • Elements can be listed, one on top of the other, in order of increasing or decreasing activity • Elements will oxidize anything below it in this series
Dalton's Law of Partial Pressures
• For a mixture of gases in a container, total pressure exerted is the sum of the pressures that each gas would exert if it were alone P(total) = P1 + P2 + P3 + ...
Types of solutions - Solid - Solid Solutions
• Formed by melting, mixing, and solidifying Ex - Steel, Brass
Kinetic Molecular Theory 1
• Gases consist of particles (molecules and/or individual atoms) that r in continuous random movement
Types of solutions - Gas - Gas Solutions
• Gases r always indefinitely soluble in one another • Air N2(g), O2(g), CO2(g), H2O(g), etc.
Halogen Displacement Redox Reactions
• Halogens bonded to themselves can take e-s from (oxidize) any halide ions that is below it in the family F2 < Cl2 < Br2 < I2 • In these reactions, H atoms in H2O r reduced, as they gain e-s to form H2 2H2O + 2e- —> H2 + 2OH- • Alkali metals, Ca, Sr, and Ba will displace H from water
Which gas more soluble in water - He or CO??
• He has weak LDF but CO is polar so can form dipole-dipole attractions and dispersion attractions • CO has more e-s, and is more polarizable, it forms stronger LDF • CO id mote soluble in water as it forms D^2 attractions and stronger LDF
Max Planck (1900)
• Hypothesized that the energy radiated fron a heated object, such as a stove element or a lightbulb filament, is emitted in discrete units, or quanta
Gases don't behave ideally at low T
• Ideal Gas Law assumes that gases experience no intermolecular FoA • At high T, KE of gas particles overcome any intermolecular FoA • At low T, gas particles move slower and r closer together. Attractions btwn molecules exist under these conditions
What assumption does the ideal gas law make about the V of gas particles in a system?
• Ideal gas law assumes that the V occupied by the gas particles in a system is negligible • V variable in the ideal gas equation is the V of empty space in the container and it assumes that the V occupied by the gas particles is 0
Substances with Lower (less +) Oxidation states than usual
• In C2O4 2-, C has an oxidation state of +3 • As C is in Group 4A, it would rather have an oxidation state of +4 • It will oxidize (lose e-s) to raise its oxidations state C2O4 2- —> CO2 • Some non-metals can raise their oxidation states by bonding with like elements • Happens when hydrochloric acid is combined with a species that is easily reduced
Identify the types of motion that individual molecules can undergo in a molecular solid
• In molecular solid, predominant motion that molecules exhibit is vibration • In some cases, rotation is possible and molecules r not free to move through translation in molecular solids
Fractional distillation was used to isolate an unknown volatile substances that had contaminated the well water at a rural property b. What can be said about the relative strengths of intermolecular interactions among and btwn the compounds in question (contaminant and water)?
• Intermolecular FoA btwn the water molecules r greater than they r btwn the contaminant molecules • This is why the vapor P of the contaminant is higher and its boiling temperature is lower • Intermolecular FoA btwn the water and contaminant r also weaker than those btwn water molecules
Non-Ideal Behavior and Condensation
• Intermolecular FoA increase as distance btwn particles decreases • Can lead to condensation at sufficiently low T and/or exceptionally high P • This applies to all gases, even those with relatively weak intermolecular forces • Condensation can occur rapidly when T of system drops - KE of gas particles is reduced and they move closer together - Under these conditions, intermolecular forces can cause particles to stick together when they collide • Condensation can also occur at high P - Gas particles r closer together and experience a higher rate of collisions - Intermolecular forces btwn particles can cause them to condense • When a gaseous system is approaching the pt where condensation will occur, FoA btwn gas particles r at a maximum • Results in the largest possible decrease in measured P, so large deviation from ideal behavior
An e- is promoted from the n=2 and the n=3 energy level in a H atom. Does the e- release or absorb energy during this transitions?
• It absorbs energy, as it moves from a lower energy level to a higher energy level
The following ?s pertain to aqueous solutions of potassium bromide b. Explain why potassium bromide dissolves in water
• KBr dissolved in water bc the cations (K+) r more attracted to the - ends of the warer molecules than they r to the anions (Br-), and anions (Br-) r more attracted to the + ends of the water molecules than they r to the catjon (K+) • Furthermore, the water molecules r more attracted to the ions than they r to other water molecules • If this was not true, the solid compound would not dissolve
Disproportionation Reactions (II)
• Like elements existing together in 2 oxidation states can undergo a redox reaction to produce a species in an intermediate oxidation state • Element must, therefore, have at least 3 oxidation states, and there must be an intermediate state that falls btwn the states of the reactants
Explain why the boiling point of water decreases as elevation increases.
• Liquid boils when its vapor P = atmospheric P. •Vapor P depends on the T of the specific liquid. • When the T of the liquid decreases, the vapor P also decreases • Atmospheric pressure decreases as elevation increases, so at higher elevations, liquid will boil at lower temperatures
Types of solutions - Solid - Liquid Solutions
• Many ionic compounds dissolve in polar solvents (ion-dipole) • Polar solids, such as glucose, dissolve in polar solvents (dipole-dipole or H-bonds) • Non-polar solids, such as mothballs, dissolve in non-polar solvents (dispersion) • Carbonated drinks H2O(L) + CO2(g) —> H3CO3(aq) • Oxygen gas dissolves in water O2(g) —> O2(aq)
Is the melting of ice to create liquid water a chemical process, physical process, or both? Justify
• Melting ice is a phase change, which is a physical process • Physical process involve changes in intermolecular forces • In this case, H-bonds r weakened
Microwave Spectroscopy
• Microwaves cause polar molecules to rotate • Each type of polar molecule has specific rotational frequencies that it can exhibit • The peaks in the microwave spectra below correlate with the different rotational frequencies for a specific polar molecule • Data from microwave spectra can be used to calculate the bond length of diatomic polar molecules and to determine the shapes of polar molecules
Collision Orientation
• Molecules must collide with an orientation that can yield a reaction
Which substance in each set has the highest melting pt? Justify ur answer using chemical principles b. NH3 or C(diamond)
• NH3 has H-bonds and LDF and Diamond is a network solid held together by covalent bonds • Covalent bonds r stronger than intermolecular forces, so C(diamond) will have a higher melting temperature
NO(g) is more soluble in water than O2 (g). Explain
• NO is larger than O2, as N has a bigger radius than O, and the bond btwn N and O is slightly polar (electronegativity different of 0.5) • Thus, NO experiences larger dispersion forces and dipole-dipole forces when it dissolves in water, making it more soluble
A gravimetric experiment was performed to determine the # of moles of sulfate, SO4 2-, that were present in a solution of NaSO4 2-. In this experiment, an excess of barium nitrate, Ba(NO3)2, was added to the solution and a precipitate formed. The resulting mixture was filtered and the precipitate was dried. The dry mass of the precipitate was measured to be 8.642 g. c) Explain why a net ionic equation is the best way to represent this reaction??
• Net ionic equation doesn't include spectator ions. as they r not involved in the reaction • only includes the aqueous species that reacted and solid product that was formed • In this experiment, only asked to determine the moles of SO4- that was present. In order to determine this quantity, we reacted sulfate with excess Ba 2+ to form solid BaSO4
Suppose u have 2 identical 1.0 L cylinders. Both cylinders r kept at exactly 25'C. 1 cylinder contains 0.3 moles of helium gas and other contains 0.3 moles of Xe gas a. Is P in cylinder containing He less than, equal to, or greater than that of Xe? Justify ur answer without performing any calculations
• P in both cylinders is same and have same V, T, and # of moles, so must have same P • According to Avogadro's Law, = V of gas at the same T and P contain = #s of gaseous particles (n1R1T1)/P1V1 = (n2R2T2)/P2V2 P1 = (P2n1R1T1V2)/(n2R2T2V1) P1 = P2, as n, R, T, and V cancel
Suppose u have 2 identical 1.0 L cylinders. Both cylinders r kept at exactly 25'C. 1 cylinder contains 0.3 moles of helium gas and other contains 0.3 moles of Xe gas b. If V of cylinder containing He increases to 2.0 L and T remains the same, what happens to the P inside cylinder? Justify ur answer by manipulating the combined gas law equation
• P inside the cylinder would decrease to half of its original value P2V2/T2 = P1V1/T1 P2V2 = P1V1 (Temperature is the same) P2(2V1) = P1V1 (V2 = 2V1) 2P2 = P1 P2 = 1/2 P1
Suppose u have 2 identical 1.0 L cylinders. Both cylinders r kept at exactly 25'C. 1 cylinder contains 0.3 moles of helium gas and other contains 0.3 moles of Xe gas b. If V of cylinder containing Xe is reduced to 0.25 L and T remains the same, what happens to the P inside cylinder? Justify ur answer by manipulating the combined gas law equation
• P would increase by a factor or 4 P2V2/T2 = P1V1/T1 P2V2 = P1V1 (Temp is the same) P2(0.25)V1 = P1V1 (V2 = 0.25V1) (0.25)P2 = P1 P2 = P1/0.25 = 4P1
Properties of Gases
• Particles r constantly moving • Expand to fill the V of the container they occupy • Form homogeneous mixtures • Low density • Highly compressible • Exert a pressure • Gases don't have definite shape or definite volume, as they r constantly moving and, ideally, there is no FoA btwn particles • Collision frequency and density of gas particles depends on P, V, and T
Redox Reactions in Acidic Solutions (I)
• Reactions btwn metals and all strong acids except Nitric Acid • H+ ions can oxidize many metals (X) • H+ pulls e-s out of the metal to form H2
Volume of Solid and Liquid Phases
• Solid and liquid phases for a particular substances normally have similar molar volumes • Density of particles is similar in both phases • Ice has a slightly larger molar V than liquid water • Most solids have a slightly smaller molar V than their liquids
Types of solutions - Liquid - Liquid Solutions
• Strong H-bonds allow these species to form a solution • CH3OH and H2O r miscible (soluble in all proportions) • Miscible solutions never become saturated • Differences in intermolecular forces can cause solution's V to differ from the sum of the volumes before mixing • Hexanol and water r not miscible - Some hexanol will dissolve in water - Solubility of hexanol limited by the long non-polar C chain • Hexane and hexanol r miscible - Hexane completely non-polar - Hexanol is mostly non-polar - Form strong LDF of attraction for one another
Strength of Acids
• Strong acids always have very weak conjugate bases • Very weak acids always have very strong conjugate bases • Acids with mid-range strengths have conjugate bases with mid-range strengths
3 notes with reactions
• Substances in lower than normal oxidation states tend to oxidize (they will oxidize if put with a strong oxidizer — stuff sheet) • If u need to decide which substance will oxidize, always pick the metal • If a substances is mentioned as a solid, don't break it into ions on the reaction side. Even if it is soluble
Like Dissolves Like
• Substances that share similar intermolecular interactions tend to be soluble or miscible in one another • Miscible - Soluble in all proportions • Miscible solutions never become saturated • Form strong LDF of attraction for one another
According to KMT, when 2 gas particles that share the same molar mass collide, is the sum of their velocities after the collision less than, equal to, or greater than the sun of their velocities before the collision? Justify
• Sum of their velocities would be the same before and after the collision • According to KMT, all collisions btwn gas particles don't change after they collide, the sum of their velocities doesn't change either • KE(initial(I))+KE(initial(II))=KE(final(I))+ KE(final(II)) • 1/2mv^2 (In. (1)) + 1/2mv^2 (In. (2)) = 1/2mv^2 (fin. (1)) + 1/2mv^2 (fin. (2)) • 1/2m(v^2 (In. 1) + v^2 (In. 2) = 1/2m(v^2 (Fin 1) + v^2 (fin. 2) • (v^2 (In. 1) + v^2 (In. 2)) = (v^2 (Fin. 1) + v^2 (Fin. 2)
A ridged 1.0 L cylinder contains 1.0 moles of O2 gas at 25'C and another ridged 1.0 L cylinder contains 1.0 moles of CH4 gas at 25'C. Is the average speed of the O2 gas particles greater than, less than, or the same as the average speed of the CH4 gas particles? Justify ur answer
• T is a measure of the average KE of the particles in a system and since both systems t at the same T, gas particles in both systems will possess the same average KE • Basic formula for KE is: KE = 1/2 mv^2. • Tells that molecules with smallest molar mass will have the largest average velocity • Atomic mass of O2 is 32 g/mol and the atomic mass of CH4 is 16 g/mol. • Since CH4 has the smaller molar mass, particles in that system will have the largest average velocity
Suppose u have 2 identical 2.0 L cylinders. Both cylinders r kept at exactly 25'C. 1 cylinder contains 0.250 moles of He, and the other contains 0.250 moles of krypton. V of these cylinder can change b. What variable must change in order to increase the average velocity of the molecules in either cylinder? Explain
• T must increase in order to increase the average speed of the atoms in either container
Suppose u have 2 identical 1.0L sealed containers. Both containers r kept at exactly 25'C. One vessel contains only Ne gas at 1.5 atm, and other contains only Xe gas at 1.9 atm. Is the value for the moles of Ne less than, equal to, or greater than that of Xe? Explain
• The # of moles of Ne must be less than # of moles of Xe • P exerted by the Ne atom is less than P exerted by the Xe atoms, when both containers r kept at the same V and T
volume adjustment for gases under high pressure
• The Ideal Gas Equation assumes that molecules don't have their own V • The V in PV = nRT is the volume of empty space in the container • Volumes of gas particles r negligible, when compared to the overall V of the container, at relatively low pressures (~ 1atm) bc they're very small and very far apart • At high P, molecules r compressed into a much smaller volume of space, and the volume occupied by the molecules becomes significant
Combustion Reactions : Combustion of Organic Compounds
• The combustion of any organic hydrocarbon in the presence of O2 produces CO2 and H2O
E(a) for Unimolecular Decomposition Reactions
• The energy required to break the bonds in the reactant is obtained during the collision with a background or solvent particle O3 + M —> O2 + O + M • For this reason, unimolecular decomposition rates increase as temperature increases
When the temperature of a solid copper pipe increase, does the motion of the free e-s increases, decrease, or remain the same?
• The free e-s would move faster when the temperature of the copper pipe increases, as the average KE of the free e-s would increase
Half-Reactions Method and Other Redox Reactions
• The half-reaction method used in the previous 2 ex. will work for any redox reactions - If there is no H2O or H+ in the balanced chemical equation, they will cancel - However H2O or H+ may appear in the half-reactions - Could be given a redox reaction and asked to write the oxidation or reduction half-reaction
Determining a Rate Law
• The rate law for an overall reaction can only be found experimentally • But, rate laws for elementary steps r predictable • For any elementary step... — aA + bB —> dD + eE — Rate = k[A]^a [B]^b • The rate of the overall reaction = rate of the slowest elementary step
Fractional Distillation
• The separation of volatile liquids in a liquid-liquid solution on the basis of boiling points • Condensation solution has a higher concentration of the component with the higher vapor pressure • If cycle of boiling and condensing is repeated enough times, complete purification of the more volatile substance can be achieved
Explain why a glass of soda at 30'C will go flat faster than a glass of soda at 5'C
• The solubility of a gas decreases as the T if the liquid solution increases • Gases tend to have weak dipole-induced dipole forces and weak LDF, as they r not very polarizable • As the KE of the particles in the solution increases, gas particles break free from these weak intermolecular forces and re-enter the gas phase
Gas solubility and pressure - Henry's law
• The solubility of a gas is directly proportional to the partial pressure of that gas above the solution • P only affects the solubility of gases
Determining a Rate Law • Fast, Reversible —> Slow
• This reaction proceeds at the rate of the slow step, but the problem is that NO3 is an intermediate so its conc is unknown • To solve this problem, we must modify the rate law
Kinetic Molecular Theory 2
• Total V of all of the gas particles in a system is negligible when compared with the total V of the system • For this reason, Ideal Gas Law assumes that V of gas particles in a system is 0
All real gases do not behave ideally when ___ and ___! Under these conditions, the ___ does not make accurate predictions!
• Under high pressures (P > 5 atm) • At low temperatures • Ideal Gas Equation (PV = nRT)
According to KMT, when 2 gas particles that have different molar masses collide, is the sum of their velocities after the collision always going to be the same? Justify
• Very unlikely that the sum of their velocities would be the same • This would only happen if each particle continued to move at the exact same speed after they collided • Sum of their KE would be the same before and after the collision, but bc they have different molar masses the sum of their velocities would most likely be different • KE = 1/2 mv^2
aminopropane, CH3CHNH2CH3, and isobutane, C4H10 • Which pure liquid has the highest boiling pt?
• aminopropane, bc both have similar LDF and same # of e-s so similar abilities to become polarized, but aminopropane forms H-bonds, which r much stronger than LDF • As a greater amount of energy is required to break stronger FoA, the boiling pt of aminopropane is higher
Molecular Orbital (MO) Theory
• Views a molecule as a whole instead of a collection of individual atoms • MOs r similar to atomic orbitals - Both have specific energy levels - Both have specific sizes and shapes - Both hold a maximum of 2 e-s that spin in opposite directions • Atomic orbitals combine to form MOs - When 2 atomic orbitals combine, 2 MOs r formed — Orbitals r always 'conserved'
Relating Volume and Temperature
• Volume of a gas can be measured at different temperatures in a laboratory. • That data can then be plotted to estimate absolute zero • If u increase the number of moles of gas in the system, the slope of the line will increase • Equal numbers of moles of any gas will produce lines with the same slope
Relating Volume and Pressure
• Volume of a gas doubles when pressure is halved
Water and Acid-Base Reactions
• Water plays an important role in many acid-base reactions that take place in aqueous solutions, as its structure allows it to accept and donate protons • H+, which has no electrons, can attach itself to one of the lone pairs on a water • H+ can be pulled off a water, which leaves a OH- with 3 lone pairs around the O atoms
Quantum Theory and Planck
• We assume that energy increases in a continuous stream • But it actually increases in discrete units. zit increases by a full quantum, or not at all • The height of each step is = to 1 quantum of energy for a certain frequency electromagnetic radiation
What is the strongest base in each following reactions? Justify based on solution equilibrium or FoA btwn particles c) 2H2O <—> OH- + H3O+
• We know that equilibrium for this reaction lies far to the left, as K(W) is 1.0x10^-14 • This means that OH- is a stronger base than H2O • OH- and H2O compete for H+ ions, and OH- wins most of the time • This drives the equilibrium to the left
Explain why the measured P of a gaseous system under conditions that r very close to those that would result in condensation will be lower than what the ideal gas law would predict. Draw a particulate representation to assist with ur explanation
• When a gaseous system is approaching the pt where condensation will occur, the FoA btwn gas particles r at a maximum. • Results in the largest possible decrease in measured P, and thus, a large deviation from ideal behavior • Attractions to neighboring gas particles will reduce impact velocities, and therefore P, by the largest possible degree under conditions that r approaching those that will result in condensation
Absorbing Photons
• When a photon is absorbed by an atom or molecule, an e- moves up one or more energy levels • Increase in energy is = to the energy of photon that was absorbed • Increase in energy is also = to the difference in energy btwn the 2 energy levels
Emitting Photons
• When a photon is emitted from an atom or molecule, an e- moves down 1 or more energy levels • Decreases in energy is = to the energy of the photon that was released • Decrease in energy is also = to the difference in energy btwn the 2 energy levels
What if u have a choice of 2 species that can be oxidized?
• When compounds contain p-block or d-block metals and non-metals with less + than usual oxidation states... • The metal will be oxidized Ex: SnCl2 Sn 2+ will be oxidized to Sn 4+
Pressure Adjustment for Gases Under High Pressures (Low Volumes)
• When gas particles r very close together, P they exert may be less than what the Ideal Gas equation would predict • Neighboring molecules exert FoA on one another when they r very close together • Such forces pull a gas molecule in the direction opposite to its motion • This reduces P resulting from impacts with the walls of the container = Low pressure system = No FoA reducing impact velocity = High pressure system = FoA reduce impact velocity
The following questions pertain to a system containing 122 (g) CO (g) in a 0.400 L container at -71.2'C b. Actual P exerted by the carbon monoxide gas is this system was found to be 145 atm. Explain why the actual P is less than what would be expected?
• When gases r behaving ideally, there r no FoA btwn particles • This means that there r no forces slowing them down before they strike the wall of a container • However, FoA do exist btwn gas particles when they r in close proximity to one another • Neighboring gas particles will pull other gas particles toward them as they r about to strike a wall • This reduces the force that particles exert on the walls of the container, thereby reducing the P
Saturated Solution
• When the solvent has dissolved the maximum amount of solute possible at a certain temperature, and some solid particles remain undissolved • an equilibrium system where solid particles continually dissolve in the solvent and dissolved particles fall out of solution
Mole Fractions and Partial Pressure
• can find partial pressure of any component in a gas mixture by multiplying the total pressure by its mole fraction
Combustion Reactions : Combustion of Elements
• combustion of any element in the presence of oxygen produces its oxide
Acids
• donate protons in aqueous solutions • Strong acids like HCl and H2SO4 experience ~100% ionization in polar solvents
If given an acidified solution of 2 ionic compounds...
• get rid of any always soluble ions and look at what is left • Decide what is getting oxidized and reduced • "Stuff sheet" includes lists of strong oxidizers — such as dichromate, permanganate, and nitrate • These reduce so then look for what could oxidize such as metals or metallic ions that could be oxidized further • The balance with half-reaction method
Nylon is saturated fatty acid. Explain why Nylon is such a strong material in terms of the interactions btwn adjacent polymers
• long chains that form strong LDF of attraction • large chainlike structures with many atoms and e-s which makes them highly polarizable • Bc overall shape of individual molecules is somewhat linear, polymers stack up well and have many contact pts which increases the strength of LDF • H-bonds can also form btwn neighboring polymers
Suppose u have 2 identical 2.0 L cylinders. Both cylinders r kept at exactly 25'C. 1 cylinder contains 0.250 moles of He, and the other contains 0.250 moles of krypton. V of these cylinder can change a. Explain why these 2 gases don't share the same velocity under these conditions
• root mean square velocity of He is greater than that of krypton • This is due to the fact that the molar mass of He is less than that of krypton • Square root of the molar mass is in the denominator of the equation and a smaller denominator (molar mass), will yield a higher velocity • The temperature is the same for both gases and the molar mass is the only variable that changes
Gas solubility and pressure - The Bends
• slope of these lines increase as intermolecular forces increase • If u ascend too quickly, the reduction in pressure causes N2(aq) to form N2(g) in ur blood (can be painful/fatal) • Deep sea divers prevent this by using He(g) in place of N2(g) - He(g) exhibits low solubility under high pressures
In a laboratory, students were given 2 unlabeled beakers and told that one of the beakers contained 1.0g of solid CaCO3 and the other contained 1.0g of solid AgNO3. They were told to devise an experiment to identify which compound was which. A student did so by adding 50 mL of distilled water to each beaker. Describe the student's observation that allowed him to identify each compound.
• solid AgNO3 would dissolve, as all nitrates r soluble in water. • CaCO3 wouldn't dissolve, as it is insoluble in water
Kinetic Molecular Theory 5
• the average kinetic energy of the molecules is proportional to the absolute temperature • Gas particles in any system kept at the same temperature will have the same average KE