Chem Ch 11 and Cumulative Final
Entropy and spontaneity
+∆S is favorable for spontaneity (more disorder) -∆S is unfavorable for spontaneity (less disorder)
How many kcal are released if 2.50 moles of H₂ reacted? N₂ + 3H₂ → 2NH₃
-19.2 kcal
Calculate enthalpy in kcal for N₂ + 3H₂ → 2NH₃ (hint: use bond dissociation energy table)
-23 kcal
How many kcal are released when 3.50 moles of N₂ react? N₂ + 3H₂ → 2NH₃
-80.5 kcal
Oxidation Number Rules
-atom in elemental state as ON of 0 -monatomic ion has ON = to its charge -binary ionic compound, ON = charge -covalent compound, atom usually has same ON as if it were monatomic --- More EN atom gets negative ON, less EN atoms get positive ONs, O is almost always 2-, H is almost always 1+ -sum of ON in neutral compound is 0, in polyatomic, it is equal to charge
How many unpaired and valence electrons in mercury
0 unpaired and 2 valence
132.0 m to km
0.1320km
Air in the trachea contains oxygen, carbon dioxide, water, and nitrogen. If the total pressure is 1.000 atm and that partial pressure of CO₂ is 0.004atm, the partial pressure of H₂O is 0.062atm, and the partial pressure of N₂ is 0.740atm, what is the partial presssure of O₂? What percentage of the gas is O₂?
0.194atm 19.4%
What is the specific heat of a metal if it takes 161 cal to raise the temperature of a 75.0 g piece by 10.0°C?
0.215 cal/J
Pressure Conversions
1 atm = 760 mm Hg = 760 torr = 14.7 psi 1 atm = 29.9 in Hg = 101,325 Pa = 101.325 kPa
1 cc (cm³) is equal to
1 mL
How many orbitals in each shell (s, p, d, and f)
1, 3, 5, and 7 respectively
1 kj = how many joules?
1,000 J
1 kcal = how many cal?
1,000 cal
WO₃ + 3H₂ → W + 3H₂O 1. How many grams of water could be made from 50.0g of WO₃? 2. How many grams of water could be made from 50.0g of H₂?
1. 11.7g 2. 447g
CH₄ + 2O₂ → 2H₂O + CO₂ 1. How many grams of CO₂ can be made from 5.00 moles of O₂? 2. How many molecules of H₂O could be made from 3.50 moles of CH₄? 3. How many moles of CH₄ are required to react with 56.0 grams of O₂
1. 110. g 2. 4.22x10²⁴ 3. 0.875 mol
Steps for assigning Oxidation numbers in binary compounds (2 elements)
1. Assign most electronegative element first; ON = negative ion charge 2. Less Electronegative element has positive ON to balance out so that total oxidation numbers equals compound's charge
Steps for assigning Oxidation numbers in non-binary compounds (more than 2 elements)
1. Assign the most EN element the negative ON equal to its ion charge 2. Assign least EN element positive ON equal to its ion chare 3. The elements with mid-EN values take ON to balance out so that total equals compound's charge
Two ways to determine whether a change of state occurs spontaneously at a given T
1. Calculate ∆G, if negative -- spontaneous, if positive -- nonspontaneous 2. Look at the temperature the change of state happens at and determine if it is above or below the temperature required
Steps to draw Lewis Structure
1. Decide the bonding pattern of molecule - Put atom with most bonds/you have fewer of in center 2. Add up total number of valence electrons available from all atoms in molecule -If positive charge, subtract those electrons -If negative charge, add those electrons 3. Draw a line (or place 2 dots) between each pair of connected atoms 4. Add lone pairs of electrons to each peripheral atom until each has octet *H only needs 1 bond, B only needs 3 5. Place any remaining electrons as lone pairs on center atom 6. If center atoms lacks octet, take lone pair from surrounding atom and make it a bonding pair to form a multiple bond
WO₃ + 3H₂ → W + 3H₂O 1. If you react 50.0 g of WO₃ and 50.0 g of H₂, what is limiting reagent? 2. What is the theoretical yield of water when reacting 50.0 g of WO₃ and 50.0 g of H₂? 3. If the reaction was done using 50.0 g of WO₃ and 50.0 g of H₂and only produced 10.0 g of water, what is the percent yield? 4. How many grams of excess reagent will be left over if theoretical yield of water is achieved? **11.7g water made from 50.0 g WO₃ and 447 g water made from H₂O**
1. WO₃ 2. 11.6 g 3. 86.2% 4. 48.72 g
Steps for balancing chemical equations
1. Write unbalanced equation with charge-balanced ionic compounds or prefixes for covalent compounds and remember diatomic elements 2. Add coefficients to balance atom numbers on each side - treat polyatomic ions as single unit if they appear on both sides 3. Reduce coefficients to lowest whole-number values
1,500,000 g to Mg
1.5 Mg
1 Mile to m
1.609 m
How many moles of H₂ are needed to react with 3.50 moles of N₂
10.5 mol
1 cubic meter to liters
1000 L
Femto f
10^-15
Hecto h
10²
Kilo k
10³
Deka da
10¹
Mega M
10⁶
Centi c
10⁻²
Milli m
10⁻³
Deci d
10⁻¹
Micro µ
10⁻⁶
Nano n
10⁻⁹
Pico p
10∧-12
How many kcal are released if 17.0 g of NH₃ is made? N₂ + 3H₂ → 2NH₃
11.5 kcal
Carbon has three naturally occurring isotopes, 98.88% is C-12 and 1.10% is C-13 and 0.02% is C-14. Calculate the atomic weight (in amu) for carbon to 4 sig figs
12.01 amu
2,550 fl oz to gal
19.9 gal
Iodine Electron Configuration
1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d10,5p⁵ Or [Kr]6s²4d¹⁰5p⁵
Linear Molecular Geometry
2 Bonded atoms, 0 lone pairs, 2 total charge clouds, 180° angles
Bent Molecular Geometry (3 charge clouds)
2 bonded atoms, 1 lone pair, 3 charge clouds, 120° angles
Bent Molecular Geometry (4 charge clouds)
2 bonded atoms, 2 lone pairs, 4 charge clouds, 109° angles
sulfur valence electrons and unpaired electrons
2 unpaired, 6 valence
1 kg to lb
2.205 lb
1 Inch to cm
2.54 cm
What is the density of a metal piece with a mass of 23,000 mg and volume of 0.00856 L in g/mL? Will it float or sink in water?
2.9 g/ml, it will sink
What is mass of a copper penny if it contains 2.94x10²² atoms of copper - round to 3sf
2.94x10²²
2.00 x 10∧10 bytes to GB
20.0 GB
2.040 x 10⁻² g to mg
20.40mg
How much energy would be required to change 25 g of liquid ether at 20.6°C into gaseous ether at 38.6°C? The specific heat of liquid ether is 0.55 cal/g°C; the specific heat of ether vapor is 0.38 cal/g°C.
2400 cal total
Trigonal Planar Molecular Geometry
3 bonded atoms, 0 lone pairs, 3 charge clouds, 120° angles
Pyramidal Molecular Geometry
3 bonded atoms, 1 lone pair, 4 charge clouds, 109° angles
1 Foot to cm
30.48 cm
Tetrahedral Molecular Geometry
4 bonded atoms, 0 lone pairs, 4 charge clouds, 109° angles
1 cal = how many joules?
4.184 J
1 kcal = how many kj
4.184 kJ
150 g of iron is at an initial temperature of 25° C. If 250 cal of energy is applied to the sample, what is the final temperature?
41°C
In an experiment, 2SO₂ + O₂ ↔ 2SO₃ at equilibrium had SO₃ concentration of 0.938M, an SO₂ concentration of 0.0620M and O₂ concentration of 0.538M, what is the equilibrium constant?
425
0.00045 L to µL
450 µ or 4.5 x 10²µ
Calculate the mass in grams of 0.500 quarts of blood with density of 103 g/ml
487 g
Calculate the volume of 50.0 g of ice with density 0.917 g/cc in mL
54.5 mL
A patient weighing 143 pounds has a prescription for Garamycin at two mg/kg, to be given by IV, every 8 hours. The drug is available in vials containing 100mg Garamycin per 50mL. How many milliliters should the nurse administer to the patient with each 8-hour dose?
64.9mL per 8 hour dose
255,000 cc to gal
67.4 gal
What is the mass (g) of 2.25 fl. oz. of liquid with a specific gravity of 1.12?
74.5 g
Which of the following have increased entropy? A. Dry ice changing from solid to gas B. Freezing liquid water to make ice C. N₂(g) + 3H₂(g) → 2NH₃(g) D. CaCO₃(s) → CaO(s) + CO₂(g) E. Dissolving sugar into water to make a sugar-water solution
A -- gas has more disorder than solid D -- 2 moles of product and 1 mole of reactant, also, gas is more disordered E -- sugar molecules become more spread out
Select all that would be classified as exothermic A. 2H₂O₂ → 2H₂O + O₂ + 48 kcal B. ∆H = +26 kcal C. 2N₂O₅ + 110 kj → 4NO₂ + O₂ D. ∆H = -424 kJ E. boiling water F. Freezing liquid water into ice G. Forming a bond H. Breaking a bond
A, D, F, and G
Group 1A (periodic table) name and characteristics
Alkali Metals, Shiny, soft metals with low melting points, react rapidly with water to form highly alkaline (basic) products, Never found in nature in pure state
Group 2A (periodic table) name and characteristics
Alkaline Earth Metals, Lustrous, silvery metals but less reactive than group 1A, Never found in nature in pure state
What is required for molecule to be symmetric?
All electron cloud regions surrounding all central atoms must be identical -- symmetric molecules never have lone pairs
Metalloids Characteristics
Along zigzag band between metals and nonmetals, share some characteristics of both metals and nonmetals
Aluminum and Oxygen Name and Equation
Aluminum Oxide Al₂O₃
Compounds
Atoms of different elements combined in specific ratio Chemical formula indicates what elements and how many atoms Can be broken into elements through chemical change
If you add a substance, which way will equilibrium shift?
Away from the side where it was added
Diatomic elements and meaning
Br, I, N, Cl, H, O, F --- always 2 when they are alone
Name BrCl₅
Bromine pentachloride
Fahrenheit to Celsius
C = (F-32)/1.8
Kelvin to Celsius
C = K - 273.15
Acetate
CH₃COO¹⁻
Cyanide
CN¹⁻
Carbonate
CO₃²⁻
Calcium and Fluorine Name and Equation
Calcium Fluoride CaF₂
Which of these (select all) would likely form a cation? 1. Calcium 2. Cesium 3. Copper 4. Bromine 5. Neon 6. Aluminum
Calcium, Cesium, Copper, and Aluminum
Assign oxidation numbers to each element, Identify oxidized element, reduced element, oxidizing agent, and reducing agent C₂H₄ (l) + KMnO₄ (aq) → CH₃COOH(aq) +MnO₂(s) + K⁺(aq)
Carbon is oxidized Manganese is reduced C₂H₄ is reducing agent KMnO₄ is oxidizing agent
Line structures
Carbons are wherever line begins or ends and at every intersection of 2 lines; hydrogen atoms are wherever they are needed so each carbon has 4 bonds, lone pairs not shown, HONC 1234 used
What is an ion
Charged particle resulting from the gain or loss of electrons from an atom
Apple Ripening Physical or Chemical?
Chemical
Changes chemical makeup of substance Physical or Chemical?
Chemical
Making water from Hydrogen and Oxygen Physical or Chemical?
Chemical
Often accompanied by indication such as color change or heat absorbed/gave off Physical or Chemical?
Chemical
Often not easily reversible Physical or Chemical?
Chemical
When a chemical bond is broken, what type of change occurs?
Chemical
Intramolecular forces
Chemical bonds like ionic bonds and Covalent bonds
Chlorate
ClO₃¹⁻
Group (periodic table)
Column
Propane Element, compound, homogeneous, or heterogeneous
Compound
Cu⁺ ion name
Copper (I)
Which has a lower melting point, covalent or ionic substance?
Covalent
Chromate
CrO₄²⁻
Dichromate
Cr₂O₇²⁻
Density Equation
Density = Mass/Volume
Naming negative ion
Dropping ending from element name and adding -ide
Valence electrons
Electrons in the outermost shell (furthest from the nucleus)
Tungsten Wedding Band Element, compound, homogeneous, or heterogeneous
Element
Isotope Symbol and Name
Element Name - Mass #
Two types of pure substances
Elements and Compounds
Melting, boiling, and sublimation (solid to gas) are endothermic or exothermic?
Endothermic
When a substance is at its phase change temperature, heat is used to overcome the intermolecular forces holding particles in that phase. The temperature remains constant until all particles have been converted Two equations for this are...
Energy = mass * heat of fusion (for melting/freezing) Energy = mass * heat of vaporization (for boiling/condensing)
Bond Dissociation Energry
Energy required to break a chemical bond
Energy (heat) equation
Energy(heat) = mass*specific heat*temperature change or q=mC∆T (∆T is final-initial temp)
Ionic equation
Equation in which dissociated ions are explicitly shown (aqueous ionic compounds dissociate) Pb²⁺ (aq) + 2NO₃⁻ (aq) + 2Na⁺ (aq) + 2I⁻ (aq) → PbI₂ (s) + 2Na⁺ (aq) + 2NO₃⁻ (aq)
Intermolecular forces
Exist between atoms and molecules, determining their physical properties; solubility, boiling points, and melting points. They are caused by the attractions between atoms or molecules due to the presence of full or partial charges caused by the unequal distribution of electrons
Freezing, condensing (gas to liqud) and deposition (gas to solid) are endothermic or exothermic?
Exothermic
Celsius to Farhenheit
F = (1.8 * C) + 32
Does something with a smaller specific heat heat up faster or slower?
Faster
What type of ions do transition elements for and how do you name them?
Form positive ions with variable charges so use roman numeral after name to indicate charge on specific ion -- except Ag is always 1+ and Zn is always 2+
Smallest unit of ionic compound
Formula Unit
Chemical formula vs Name
Formula is symbols and subscripts, name is written out words
Elements
Found on periodic table Cannot be broken down into anything simpler
How do nonmetals form ions
Gain electrons to have 8 valence electrons and for positive ions
London Dispersion Forces
Get stronger as size (or number of electrongs) increases; results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles
What cation will acids have?
H+
Bicarbonate
HCO₃¹⁻
Group 7A (periodic table) name and characteristics
Halogens, Colorful and corrosive nonmetals, found in nature in combination with other elements, halogen from greek word meaning salt
Shaker filled with cinnamon sugar Element, compound, homogeneous, or heterogeneous
Heterogeneous
Do polar molecules experience a higher or lower boiling point than nonpolar molecules?
Higher -- stronger IMF
Gasoline Element, compound, homogeneous, or heterogeneous
Homogeneous
Two Types of Mixtures
Homogeneous and heterogeneous
Difference between homogeneous and heterogeneous
Homogeneous is uniform Heterogeneous is not uniform
HONC 1234 meaning
Hydrogen, oxygen, nitrogen, and carbon make 1, 2, 3, and 4 bonds respectively
Where are ionic bonds found?
In ionic compounds
A child weighing 30 kg arrives at the clinic with diffuse itching as the result of an allergic reaction to an insect bite. The doctor prescribes 25 mg of benedryl to be taken 3 times a day. The correct pediatric does is 5 mg/kg/day. Is the prescribed correct? If not, what is the correct dose (at 3 times) per day?
Incorrect, Need 50 mg/dose
Lanthanides and Actinides (periodic table)
Inner Transition Metals (2 rows at botton of table)
How to name bases
Ionic compound naming rules
Differences between ionic bonds and covalent bonds
Ionic: Depends on ionization energy, electron affinity, and electron configurations Covalent: Depends on electron configuration and differences in electronegativities
Differences between ionic compounds and molecular compounds
Ionic: balance charges of cations and anions, soluble in polar solvents, high melting points, solution conductivity Covalent/Molecular: represented by lewis structures, polar or nonpolar, low melting and boiling points
Does an item float or sink if its density is greater than water's?
It sinks
Equilibrium Constant
K -- indicates the positions of the reaction at equilibrium and calculated by plugging in concentrations of reactants and products at equilibrium into equilibrium equation
Celsius to Kelvin
K = C + 273.15
Is the energy required to break an intermolecular force greater than or less than the energy required to break a chemical bond?
Less than
Ionic name Lithium
Lithium ion
How do main group metals form ions
Lose Valence electrons and form positive ions (Main group elements in same group for same ion charge)
If atmospheric pressure is lower, will the boiling temperature be higher or lower?
Lower
Group A (periodic table)
Main Group Elements
Air Element, compound, homogeneous, or heterogeneous
Mixture - debatable on what type
Permanganate
MnO₄¹⁻
Hydrogen Bond IMF
Moderate Strength (2-10kcal/mol, 8-40kJ/mol); occurs between molecules with O-H, N-H, and/or F-H bonds
More unequally electrons shared: more or less polar bond?
More polar
Ammonium
NH₄¹⁺
Nitrate
NO₃¹⁻
Naming Positive Ions
Named with name of element and word ion
Dipole CH₂O
Net dipole toward O
Zero at beginning of decimal number Significant?
No
Zero used as placeholder in large number with no decimal point Significant?
No
Group 8A (periodic table) name and characteristics
Noble Gases, Colorless gases, lack chemical reactivity
If dipoles cancel, is molecule polar or nonpolar
Nonpolar (if they do not, it is polar)
Drawing Orbital Diagrams
Number of boxes = number of orbitals, fill each with one first, then fill with rest of electrons
Unpaired Electrons
Number of electrons not paired up in orbitals
Atomic Number
Number of protons (and electrons)
How to determine unpaired electrons
Number of single electrons in orbital diagram
What does group number of main group elements tell you about valence electrons?
Number of valence electrons
HPO₄²⁻ Oxidation Numbers
O = -2 H = +1 P = +5
N₂O₅ Oxidation Numbers
O= -2 N= +5
Hypochlorite
OCl¹⁻
What ion do bases have?
OH-
Hydroxide
OH¹⁻
Phosphate
PO₄³⁻
Pa Equation
Pa = moles A/total moles (or %A) * total pressure %A = Pa/Ptotal * 100
H-bond acceptor
Partial negative F, O, or N bonded to H
H-bond donor
Partial positive bonded to F, O, or N
Ionic name Phosphorus
Phosphide
Changes of state or particle size Physical or Chemical?
Physical
Dissolving salt in water Physical or Chemical?
Physical
Does not alter chemical makeup of substance Physical or Chemical?
Physical
Grinding Metal Physical or Chemical?
Physical
Often are easily reversible Physical or Chemical?
Physical
When intermolecular forces are broken, is it a physical or chemical change?
Physical
How to tell difference between precipitation, neutralization, and redox
Precipitation: has aqueous parts with a solid in products Neutralization: has acid/base Redox: typically has element alone
Mass #
Protons + Neutrons
What to do if polyatomic ion needs subscript in ionic compound?
Put polyatomic ion in parentheses and add subscript outside of it
Boyle's Law
P₁V₁=P₂V₂
Formula for Tetraphosphorus decaoxide
P₄O₁₀
What does a balanced equation tell us?
Relative amounts of product and reactants (moles can also be inferred in stoich problems)
Period (periodic table)
Row
Sulfate
SO₄²⁻
What determines the strength of IMF for non-polar molecules?
Size of the molecule (or # of electrons), larger molecule = stronger IMF
Atomic Radius trend
Smaller to right of periodic table
Acetic acid has melting point of 16.7°C and boiling point of 118°C. What state of matter will it be at 10°C?
Solid
Metal Characteristics
Solid at room temp (except mercury), lustrous, good conductors of heat and electricity, malleable
Specific Gravity Equation
Specific Gravity = Density of Substance/Density of H₂O at the same temperature (assumed to be 1.00 g/mL typcially)
How to write ionic coumpounds
Subscripts used to increase ion numbers so charge equal Subscripts must be reduced to lowest ration possible Cation always is first Ionic compound name is Cation element name (without ion) followed by anion name
Weighted Average Atomic Mass calculation
Sum of each isotope mass # * % Abundance
How to determine valence electrons
Sum of electrons in largest (number) shell
Dalton's Law
The total pressure exerted by a gas mixture of (Ptotal) is the sum of the partial pressures of the components in the mixture: Ptotal = Pgas1 + Pgas2 + Pgas3 +... Says that the percentage (moles A/total moles) of each gas in the mixture is equal to the pressure percentage that each gas contributes (Pa/Ptotal)
Stronger IMF between molecules mean more energy is required to change state. What does this mean for melting and boiling points?
They are higher
Sn⁴⁺ ion name
Tin (IV)
If you increase pressure, which way will the equilibrium shift?
To the side of the reaction with fewer moles of gas (to reduce squishing particles close together)
If you remove a substance, which way will equilibrium shift?
To the side where the substance was removed
Group B (periodic table)
Transition Metals (middle of table)
Which of the following is not an element 1. Carbon 2. Oxygen 3. Hydrogen 4. Water
Water
London Dispersion IMF
Weak (0.5-2.5kcal/mol, 2-10kJ/mol); occurs between all molecules, strength depends on size
Dipole-Dipole IMF
Weak (1kcal/mol, 4kJ/mol); occurs between polar molecules
Atomic mass
Weighted average of all isotopes
LeChatlier's Principle
When a stress is applied to a system at equilibrium, the equilibrium shifts to relieve the stress
Equilibrium
When the forward and reverse reaction rates become equal and the concentrations of reactants and products have reached constant levels (rate forwards = rate backwards)
Naming binary covalent compounds
Written with nonmetal further left is first, use prefix (if subscript is not one) to indicate number of atoms; The second element has ending -ide along with prefix --even if it is one
Any digit in coefficient of scientific notation Significant?
Yes
Are all changes of state temperature dependent?
Yes
If there are 45 people in a room and 5 people in the hallway which 3 people per minute moving from the room to the hallway and 3 people per minute moving from the hallway to the room, is this at equilibrium
Yes
Nonzero Digit Significant?
Yes
Zero at the end of a decimal number Significant?
Yes
Zero between nonzero digits Significant?
Yes
Can molecule with polar bonds be non-polar?
Yes - if molecule is symmetric
What must total charge equal in ionic compound?
Zero
Acid name if anion ends in -ite
________ous acid
Acid name if anion ends in -ate
_______ic acid
Melting ice has ∆H = +1.44 kcal and ∆S = +5.27 cal/k Which of the following are true? a. melting is endothermic b. melting is exothermic c. melting results in an increase in entropy d. melting results in a decrease in entropy e. melting happens spontaneously at all temperatures f. melting happens nonspontaneously at all temperatures g. melting happens spontaneously only at temperatures above 0°C h. melting happens spontaneously only at temperatures below 0°C
a, c, g (when ∆H is unfavorable but ∆S is, reaction only occurs spontaneously at "high" temperatures)
Compare the boiling points and structures of CO₂ and CH₂O. a. Which has a stronger IMF? b. How do these molecules differ from each other?
a. CH₂O because it has a higher boiling point b. CO₂ is nonpolar, CH₂O is polar
Reaction has ∆H = -17.4 kcal and ∆S = +27.2 cal/k a. Is this reaction exothermic or endothermic? b. Does entropy increase or decrease? c. At which temperatures is this reaction spontaneous?
a. Exothermic b. Increase c. All temperatures
In exothermic reactions... a. ∆H (enthalpy) <0, is this favorable or unfavorable for spontaneity? b. ∆S (entropy) <0, is this favorable or unfavorable for spontaneity? ...Why?
a. Favorable - release heat as molecules move slower b. Unfavorable - molecules become more orderly arranged
Compare HBr and HF a. Which will have larger LDF? b. Which has stronger IMF, based on boiling point?
a. HBr is bigger = stronger LDF b. HF has higher boiling point = stronger IMF
Fe³⁺ + SCN⁻ ↔FeSCN²⁺ a. If you have 2 moles Fe, 6 moles of SCN, and 3 moles of FeSCN, what is the equilibrium constant? Does it favor forward or reverse reaction? b. If you have 6 moles Fe, 7 moles SCN, and 3 moles FeSCN, what is Q? Do you need to change reactants into products or change products into reactants for equilibrium to be restored? c. How many moles of each will there be once equilibrium is restored? d. If reactants are removed an you have 2 Fe, 1 SCN, and 5 FeSCN, what is Q, and how do you restore equilibrium? e. What should the mixture be after you restore equilibrium? f. If you had an equilibrium mixture with 5Fe and 8SCN, how many FeSCN molecules should you have?
a. K(eq) = 0.25, favors reverse b. Q = 0.071, change reactants into products c. 4 moles Fe, 5 moles SCN, 5 moles FeSCN d. Q = 1.7, Change products into reactants e. 4 Fe, 3 SCN, 3 FeSCN f. 10
Melting ice has ∆H = +1.44 kcal and ∆S = +5.27 cal/k a. Will this reaction be spontaneous at -10.0°C? b. What would ∆H and ∆S be for the reverse reaction (freezing)? c. Will the reverse reaction be spontaneous at -10.0°C?
a. No b. ∆H = -1.44 kcal and ∆S = -5.27 cal/k c. Yes -- since melting is only spontaneous above 273K, the opposite reaction will only be spontaneous below 273K
CH₄(g) + H₂O(g) ↔ 3H₂ + CO(g) Determine if the "stress" will shift left (to reactants), right (to products), or have no effect a. CO removed b. H₂ added c. Pressure increased d. CH₄ added e. Heat added f. H₂O removed
a. Right shift b. Left shift c. Left shift d. Right shift e. Right shift f. Left shift
A reaction has ∆H = -844 kJ and ∆S = -1650 J/K a. Is it endothermic or exothermic? b. Does entropy increase or decrease? c. At what temperatures is this reaction spontaneous? d. Calculate ∆G at 275°C
a. exothermic b. decrease c. temperatures below 512K d. +60.2 kJ
What does it mean if... a. K is much small than 0.001 b. K is between 0.001 and 1 c. K is between 1 and 1,000 d. K is much larger than 1,000
a. only reactants are present at equilibrium; essentially no reaction occurs b. More reactants than products are present at equilibrium (reverse reaction favored) c. More products than reactants are present at equilibrium (forward reaction favored) d. Only products are present at equilibrium; reaction goes
a. Q=K b. Q<K c. Q>K
a. reaction is at equilibrium b. reaction is going backwards more than forwards and must shift forward to restore equilibrium c. reaction is going forwards more than backwards and must shift backward to restore equilibrium
In endothermic reactions... a. ∆H (enthalpy) > 0, is this favorable or unfavorable for spontaneity? b. ∆S (entropy) > 0, is this favorable or unfavorable for spontaneity? ...Why
a. unfavorable - they require heat input as molecules move faster b. favorable - they become more random as molecules become more spread out
Factors that affect reaction rate
activation energy (energy needed to start reaction - can be lowered by a catalyst), concentration of reactants, and temperature (affects speed of particles)
Specific heat
amount of energy required to change the temperature of 1 g of a substance by 1°C
actual yield
amount of product actually obtained in reaction
theoretical yield
amount of product that can be made before limiting reagent runs out
Polar Covalent bond
atoms have EN difference of 0.5-2, electrons shared unequally, more EN atom hogs electrons
Nonpolar Covalent bond
atoms sharing elections with EN difference of <0.5, electrons shared equally
How to calculate excess reagent
calculate amount of it needed to make the theoretical yield of product; then subtract the amount used from starting quantity
Equation for the temperature at which a reaction changes spontaneity
can be calculated at the T vale for which ∆G = 0 so T=∆H-∆S
Ionic bonds are between
cation and anion
Formal Charge
charge any atom would have if the bonding electrons were shared exactly equally, MUST add up to equal molecule's charge
10 prefix
deca-
-∆S
decrease in disorder
2 prefix
di-
Ionic bond
electrons not shared at all (EN difference >2
reverse of exothermic reaction
endothermic
Enthalpy and spontaneity
endothermic (+∆H) is unfavorable for spontaneity exothermic (-∆H) is favorable for spontaneity
What results in positive q and positive ∆T
energy addition
Electron affinity definition and trend
energy released on dding an electron to single atom in gaseous state, the ease with which an atom gains an electron, Gets larger to right of periodic table
What results in negative q and negative ∆T
energy removal
Heat of Vaporization/Fusion
energy required to break intermolecular forces
What do ∆H values indicate
enthalpy of reaction; energy associated with a reaction
Net ionic equation
equation that has the spectator ions removed
reverse of an endothermic reaction
exothermic
What does subscript tell me about moles and atoms?
for every one mole of a compound, the subscript indicates the number of moles of an element; and for every one molecule of a compound, the subscript indicates how many atoms of an element there are
Reduction
gain of one or more electrons by an atom
Endothermic Reaction
heat is absorbed (energy is positive) or ∆H is positive; heat is a reactant
Exothermic Reaction
heat is released (energy is negative) or ∆H is negative; heat is a product
7 prefix
hepta-
6 prefix
hexa-
What do coefficients indicate?
how many moles of reactants react and how many moles of product are formed used to convert from moles to moles of two substances
Acid name if anion ends in -ide
hydro_______ic acid
+∆S
increase in disorder
Precipitate
insoluble solid product
Spectator Ions
ions that are unchanged on both sides of the reaction arrow
Oxidation
loss of one or more electrons by an atom
Molar mass
mass of one mole of substance in grams used to change between moles and grams calculated by adding masses of atoms in chemical formula from periodic table SHOULD BE ROUNDED TO ONE DECIMAL PLACE
Entropy
measure of the amount of disorder in a system; measured in cal/(mol*K) OR J/(mol*K)
Entropy Change ∆S
measure of the increase or decrease of disorder as a chemical reaction or physical change occurs: affected by many things such as temperature, state of matter, and number of particles present
Electronegativity (EN)
measures how much an atom can attract electrons
Free-energy change (∆G)
measures the change in free energy as a chemical reaction or physical change occurs (takes into account ∆H and ∆S and temperature)
Give molar mass, number of moles, number of atoms of oxygen, a number of molecules for 48g of sulfur trioxide
molar mass = 80.1 g/mol moles = .60 mol atoms of oxygen = 1.1x10²⁴ molecules = 3.6x10²³
1 prefix
mono-
+∆G
non-spontaneous (endergonic)
9 prefix
nona-
Avagadro's number
number of particles of substance in one mole quantity 6.022x10²³ Used to change between moles to atoms or molecules One mole of element has 6.022x10²³ atoms One mole of compound has 6.022x10²³ molecules
8 prefix
octa-
How to draw electron dot symbols
one dot=one valence electron and each side gets an electron before any side gets two
Anions (negative) form when
one or more electrons are gained
Cations (positive) form when
one or more electrons are lost
Precipitation reactions
one product is insoluble, forming a solid (soluble product dissociates into spectator ions)
Ionic compound formed from
oppositely charged ions
5 prefix
penta-
Percent yield equation
percent yield = actual yield/theoretical yield times 100
Nonmetal Characteristics
poor conductors of heat and electricity, eleven are gases at room temp, six are brittle solids, one is liquid
Partial pressure
pressure exerted by each gas in a mixture and is the same pressure that the gas would exert if it were alone
Reducing agent
reactant that contains the oxidized element
Oxidizing agent
reactant that contains the reduced element
Limiting reagant
reactant that runs out first and limits amount of product made
What qualifies as a substance in an equilibrium equation?
reactant, product, or heat
Neutralization reactions
reactants are an acid (H+ cation) and a base (OH-) anion; products are water and an ionic compound (salt) formed from base cation and acid anion when cations switch places (double replacement)
excess reagent(s)
reactants left over after the theoretical yield is reached
Oxidation-Reduction (Redox) Reactions
reactions in which electrons are transferred
Q = reaction quotient How to calculate
same way as K; it will tell you where the reaction is at with respect to equilibrium
Reaction rate
speed at which a chemical reaction takes place; depends on number and force of collisions between molecules and molecule orientation upon collision
-∆G
spontaneous (exergonic)
Resonance Structures
structures that differ in the placement of multiple bonds, but not in the arrangement of atoms, denoted with a ↔
4 prefix
tetra-
Which ion are acids named from?
the anion
Ionization Energy definition and trend
the ease with which an atom loses an electron to form cation/ energy required to remove valence electron from single atom in gaseous state, Gets larger to right of periodic table
Given ∆H values are per coefficient mole of each reactant and product; What can this determine?
the heat absorbed or released for the reaction of a specific amount of reactant or product
Vapor Pressure
the partial pressure of vapor molecules in equilibrium with a liquid; increases with temperature. once vapor pressure = atmospheric pressure, boiling occurs
What does electron configuration list?
the subshells and how many electrons are in each one
In changes of state, what do molecules do?
they get farther apart or closer together
3 prefix
tri-
Double Replacement Reactions
two ionic reactants, cations trade places for two new ionic products
Calculate formal charge
valence electrons - (1/2 the shared electrons + all lone electrons)--- do this for each atom in the molecule to determine which resonance structure is best
∆G equation
∆G = ∆H - T∆S
∆H Equation
∆H = [∑(Bond Dissociation Energies)reactants - ∑(Bond Dissociation Energies)products]