Chemistry 111 Final Exam
Always think mole as a...
"Bridge" to connect the "microscopic" world (particles such as atoms, molecules, ions, etc.) with the "macroscopic" world (large scale, such as g-or kg-, quantities)!
There are two approaches in solving problems
"Have & Need" approach and "Smaller-Amount" approach. If the question is asking for the amount of product(s) possible (without asking the identity of the limiting reactant),the "Smaller-Amount" approach is a quicker way. However, you will be getting the same conclusions/answers using the "Have & Need" approach.
The old Chemistry joke:
"You're positive, you must have lost electrons".
Formulas for Percent Concentrations
% (m/m) % (v/v) % (m/v) If the percent concentrations are given, they can be used as conversion factors.
Scientific notations in your calculators
(EXP or EE buttons are used for "× 10" part and you simply add a number for the power of 10, in most of the calculators). Check with your own calculator!
Calorimeter
- A calorimeter is a device used to measure the amount of heat involved in a chemical or physical process. - Many processes measured in a calorimeter occur in solution. - If the reaction is exothermic, the heat produced by the reaction is absorbed by the solution. - If the reaction is endothermic, the heat required for the reaction to occur is provided by the solution.
Endothermic
- A change that absorbs heat - Endothermic = heat "enters" into the system (as a reactant)
Exothermic
- A change that releases heat - Exothermic = heat "exits" out to the surroundings (as a product).
Across a period
- A stronger pull (higher effective nuclear charge) is experienced by the outermost electrons, drawing them closer to the nucleus. - The size of the atom (and its covalent radius) decreases across a period.
Dalton's Atomic Theory
- All matter is composed of extremely small particles called atoms. -> Dalton assumed atoms to be indivisible. This isn't quite so, as we will see with subatomic particles and radioactivity. - All atoms of a given element are alike, but atoms of one element differ from the atoms of any other element. -> Dalton assumed that all the atoms of a given element were identical in all respects, including mass. This is now known to be incorrect, as we will see in the next section. - Compounds are formed when atoms of different elements combine in fixed proportions. -> Unmodified: The numbers of each kind of atom in a compound usually form a simple ratio. For example, the ratio of carbon atoms to oxygen atoms is 1:1 in carbon monoxide and 1:2 in carbon dioxide. - A chemical reaction involves a rearrangement of atoms. No atoms are created or destroyed or broken apart in a chemical reaction. -> Unmodified for chemical reactions. Atoms are broken apart in nuclear reactions.
State functions
- Are properties that are determined by the state of the system, regardless of how that condition was achieved i.e. state functions are path-independent properties. - The magnitude of change depends only on the initial and final states of the system. Energy Pressure Volume Temperature
Isoelectronic species
- Atoms and ions that have the same electron configuration are said to be isoelectronic. - Examples of isoelectronic species: N3-, O2-, F-, Ne, Na+, Mg2+, and Al3+ (1s22s22p6) P3-, S2-, Cl-, Ar, K+, Ca2+, and Sc3+ ([Ne]3s23p6) - For atoms or ions that are isoelectronic, the number of protons determines the size. - The greater the nuclear charge, the smaller the radius in a series of isoelectronic ions and atoms.
Make sure you know the two mole conversion factors:
- Avogadro's number (NA): 1 mol = 6.02 ×10^23 particles (particles = atoms, or ions, or molecules, or .... - check your question), - Molar mass (MM): 1 mol = formula mass in grams (a.k.a. gram formula mass; GFM). Use Periodic table to get GFM for any element. - Subscripts in the molecular formula: the subscripts indicate the number of atoms of elements in a molecule of the compound or number of moles of atoms of elements in one mole of compound. Visualize the "Car-and-Wheels" example. 1 car = 4 wheels; 1 mol cars = 4 mol wheels! For example, 1 NH3 "car" = 3H "wheels" and 1 mole NH3 "car" = 3 mol H "wheels".
The basic mole relationships and getting conversion factors from them
- Avogadro's number (NA): 1 mol =6.02 ×1023particles (particles = atoms, or ions, or molecules, or .... check your question). - Molar mass (MM): 1 mol = formula mass in grams (a.k.a. gram formula mass; GFM). Use Periodic table to get GFM for any element. - Subscripts in the molecular formula: the subscripts indicate the number of atoms of elements in a molecule of the compound or number of moles of atoms of elements in one mole of compound. Visualize the "Car-and-Wheels" example. 1 car = 4 wheels; 1 mol cars= 4 mol wheels! For example, 1 NH3"car" = 3 H "wheels" and 1 mole NH3"car" = 3 mol H "wheels".
Why are proper breathing techniques very important in scuba diving?
- Because the deeper you dive, the higher the atmosphere you are in. - When diving into a higher atmosphere, the volume of air spaces will get smaller and the molecules in those spaces will become more compact.
Brown Tiny Cat Mnemonic device: Brown Tiny Cat Plays Great Violin At Ten PM.
- Boyle's law has Temperature (and number of moles) constant - Charles' law has Pressure (and number of moles) constant - Gay-Lussac's law has Volume (and number of moles) constant - Avogadro's law has Temperature and Pressure constant.
Standard enthalpy (Indirect method)
- Carefully check the net reaction equation and remember two things: "Order" and "Numbers". - When an equation is reverse, the sign for∆𝐻o changes.
Enthalpy Change (DH)
- Chemists usually perform experiments in open containers under normal atmospheric conditions, so the external pressure is constant. - At these conditions, if the only work done is caused by expansion or contraction, then the heat flow (qp) and the enthalpy change (ΔH) for the process are equal. - This makes enthalpy the most convenient choice for determining heat. - Enthalpy values for specific substances cannot be measured directly; only enthalpy changes (ΔH) for chemical or physical processes can be determined.
Calorimetry Principles
- Consider a hot piece of metal (M) and cool water (W). - If the metal is placed in the water within a calorimeter, heat will transfer from M to W.• - The temperature of M will decrease.• - The temperature of W will increase. - Eventually, thermal equilibrium will be reached and both objects will have the same temperature. The net change in heat is zero qm + qw = 0 Heat gained by M is equal to the heat lost by W. qm = -qw Heat lost = heat gained (no net change in heat content of the universe).
Valence Bond Theory
- Covalent bonds are formed by sharing of electron from overlapping atomic orbitals. - To form a covalent bond, an atom must have an unpaired electron. - The number of bonds formed by an atom is determined by the number of unpaired electrons. - This theory works well for explaining the bonding in diatomic molecules with only single bonds. - This theory also works well for explaining the lack of bonding experienced by the noble gases.
Classification of matter
- Depending on its properties, a given substance can be classified as a homogeneous mixture, a heterogeneous mixture, a compound, or an element.
Dalton's law of partial pressures states that the total pressure
- Depends on the total number of gas particles, not on the types of particles. - Exerted by a gas mixture is the sum of the partial pressures of those gases. P Total = PA + PB + PC +..
Law of conversation of energy
- During a chemical or physical change, energy can be neither created nor destroyed, although its form can change. - In other words, the total energy content of the universe is constant.
First Law of Thermodynamics
- Energy can be transferred and transformed, but it cannot be created or destroyed. - The association between the change in internal energy (ΔU), heat (q), and work (w). ΔU = q + w - ΔU is the change in internal energy of a system - q is the heat exchange between the system and the surroundings - w is the work done on (or by) the system
Planck's Theory
- Energy emitted or absorbed is NOT continuous but is "discrete". - The absorbed or emitted energy can have only specific or discrete values or is "quantized." Planck's equation: E light = hv Planck's constant (h) = 6.63 x 10^-34 J*s
For atomic size, use...
- Francium (Fr) and Helium (He) as reference atoms. - Is your element close to helium or francium? - Do NOT guess! Use the logic!!
Kinetic Molecular Theory (KMT) Summary
- Gases are made of particles whose separation is greater than the size of the particles. - Particles are in constant random motion. - Average kinetic energy is proportional to the gas temperature.
Ideal gases
- Gases are made up of tiny molecules - Gases molecules are always in rapid motion - Gas molecules have no attraction for one another - Gas molecules undergo elastic collisions; they do not lose kinetic energy - The average kinetic energy of a gas molecule is proportional to its temperature.
Physical Characteristics of Gases
- Gases assume the volume and shape of their containers. - Gas particles moving in random directions at high speeds cause a gas to fill the entire volume of a container. - The average molecule in air moves at the speed of > 1000 mph! - Gases are the most compressible state of matter. - Gases have much lower densities than liquids and solids.
General classification of elements:
- Group 1 (1A): Alkali metals [Note: H is an exception; it is a nonmetal.] - Group 2 (2A): Alkaline earth metals - Group 17 (7A): Halogens - Group 18 (8A): Noble gases (also known as inert gases) - Main group elements (or representative elements) = all Group "A" elements. - Transition metals = all Group "B" elements.
Hess's law
- If a process can be written as the sum of several stepwise processes, the enthalpy change of the total process equals the sum of the enthalpy changes of the various steps. - Hess's law is a manifestation that enthalpy is a state function. - Enthalpy changes depend only on where a chemical process starts and ends, not on the path it takes from start to finish.
The periodic table tendency for effective nuclear charge...
- Increase across a period (due to increasing nuclear charge with no accompanying increase in shielding effect). - Decrease down a group (although nuclear charge increases down a group, shielding effect more than counters its effect)
Bond Order
- Indicates how stable a molecule is. - The higher the bond order, the more stable a molecule is.
Physical property
- Is a characteristic of matter that is not associated with a change in its chemical composition. Examples: density, color, hardness, melting and boiling points, and electrical conductivity.
Paramagnetism
- Is a result of a molecule's electron configuration. - Species that contain one or more unpaired electrons are paramagnetic. These species are attracted to magnetic fields.
Energy
- Is measured in terms of its capacity to perform work or to produce/transfer heat. - Work (w): Energy is used to cause an object that has mass to move. Work = Force x Distance - Heat (q): Quantity of thermal energy transferred between two bodies that are at different temperatures. Heat flows from hotter to cooler system.
Vapor Pressure and Boiling Point
- Is the pressure above a liquid at equilibrium in a closed container. - At the boiling point becomes equal to the external pressure. - In order for a liquid to boil, the vapor pressure must be equal to or higher than the atmospheric pressure.
Atmospheric pressure
- Is the pressure exerted by a column of air from the top of the atmosphere to the surface of the Earth. - Is about 1 atmosphere or a little less at sea level.
Effective nuclear charge (Zeff)
- Is the pull exerted on a specific electron by the nucleus, taking into account any electron-electron repulsions. - For hydrogen, there is only one electron and so the nuclear charge (Z) and the effective nuclear charge (Zeff) are equal. - For all other atoms, the electron of interest are partially shielded from the pull of the nucleus by the other electron(s) present. - Core electrons are adept at shielding, while electrons in the same valence shell do not block the nuclear attraction experienced by each other as efficiently. - Each time we move from one element to the next across a period, Z increases by one, but the shielding increases only slightly due to electrons being added only to the valence shell. - Zeff increases as we move from left to right across a period.
Bomb calorimeters
- Is used to measure the energy produced by reactions that yield large amounts of heat and gaseous products, such as combustion reactions. - This type of calorimeter consists of a robust steel container (the "bomb") that contains the reactants and is itself submerged in water. - The energy produced by the reaction is trapped in the steel bomb and the surrounding water.
Why is high specific heat of water important for us?
- It absorbs a lot of heat before it begins to get hot. The high heat capacity of water also helps regulate the rate at which air changes temperature, which is why there is temperature . - Water is able to absorb a high amount of heat before increasing in temperature, allowing humans to maintain body temperature.
Difference between mass and weight
- Mass -> is a measure of the amount of matter in an object. - Weight -> refers to the force that gravity exerts on an object. An object's mass is the same on the earth and the moon but its weight is different.
The mass number, isotopes, and isotope symbols.
- Mass number = total number particles present in the nucleus (protons and neutrons). This makes sense because the atomic nucleus contains more than 99.9% of the mass of an atom. - Why can you not find mass number information on the periodic table? - Should be able to identify if two or more species are isotopes of the same element or not (isotopes have same atomic numbers but different mass numbers). - Should be able to figure out the # of protons, # of electrons, and # of neutrons using isotope symbol (also known as atomic symbol). Make sure you know all the components of an isotope symbol. For example, one of the isotopes of sodium metal can be represented with a symbol: Na 23 (top) & 11 (bottom). This gives atomic # = 11, mass # = 23, # of e- = 11, # of p+= 11 and # of n0= 23-11 = 12.
Hybridization of atomic orbitals.
- Mixing of two or more atomic orbitals to form a new set of hybrid orbitals. - Mix at least 2 nonequivalent atomic orbitals (e.g.s and p). Hybrid orbitals have very different shapes from original atomic orbitals. - Number of hybrid orbitals is equal to number of pure atomic orbitals used in the hybridization process. - Bonding in other molecules, such as CH4, is best explained with hybrid orbitals.
Species that are exception to octet rule
- Odd number of valence e-s. (NO, NO2, etc) - Electron deficient species (incomplete octets; BeH2, BeCl2, BF3, etc.) - Expanded octet (applicable for atoms with principal quantum number (n) > 2 i.e. PCl5, SF6, IF7 etc.).
Heat capacity (C)
- Of a body of matter is the quantity of heat (q) it absorbs or releases when it experiences a temperature change (ΔT) of 1 °C (or 1 kelvin): C = q/ΔT - Heat capacity is an extensive property. - For example, the heat capacity of a large cast iron pan is greater than the heat capacity of a small cast iron pan.
Specific heat capacity (c)
- Of a substance, commonly called its "specific heat," is the quantity of heat required to raise the temperature of 1 gram of a substance by 1 °C (or 1 kelvin): c = q/mΔT - Specific heat capacity is an intensive property— it only depends on the identity of the substance, not the amount. - For example, the specific heat capacity of a large and small cast iron pan are identical.
Whole-body calorimeters
- Of various designs are large enough to hold a human being. - These calorimeters are used to measure the metabolism of individuals under different conditions: -> Environmental conditions -> Dietary regimes -> Health conditions, such as diabetes - A nutritional calorie (Calorie) is the energy unit used to quantify the amount of energy derived from the metabolism of foods.
Polarity
- Partial charges or dipole moments (resulting from bond polarity) are important in determining molecular polarity. But, all bonds must be considered. If the vectors of partial charge/dipole moment end up canceling out, then the molecule may not be polar. - In order to predict dipole moments, you have to examine the geometry of the bonds which you can find via valence shell electron-pair repulsion (VSEPR) theory. This theory starts with the idea that electron pairs in the valence shell of an atom repel each other. The electron pairs around an atom will thus orient themselves in order to minimize repulsive forces.
Non-State Functions
- Path-dependent properties Work (w) = Force (F) x distance (d)
ΔH has a positive or negative value
- Positive ΔH: energy enters (or is absorbed) as reactant -endothermic! - Negative ΔH: energy exits (or is removed) as product -exothermic! - Should be able to interpret the energy diagrams. Check if ΔH is positive or negative! - Use the money example to visualize (money enters the bank account, say after you receive your paycheck, and money exits the bank account, say when you make payments during shopping).
Properties of a Gas Sample
- Pressure (P) = force with which the gas molecules hit the sides of the container. - Volume (V) = space in which the gas molecules can move. - Temperature (T) = corresponds to the speed of the gas molecules (expressed in Kelvin). - Amount (n) = quantity of gas present in the container (number of moles).
The names, symbols, charges and general locations of three subatomic particles:
- Protons -> Symbol: p+ -> Charge: Positive -> Location: Nucleus - Neutrons -> Symbol: n0 -> Charge: Neutral -> Location: Nucleus - Electrons -> Symbol: e- -> Charge: Negative -> Location: Electron cloud Must be able to visualize an atom based on electron cloud model.
States of matter
- Solid -> is rigid and possesses a definite shape. - Liquid -> Flows and takes the shape of its container. - Gas -> Takes both the shape and volume of its container. - Plasma -> A gaseous state of matter that contains an appreciable amount of electrically charged particles. Plasma has unique properties distinct from ordinary gases. Plasma is found in certain high-temperature environments. -> Naturally: Stars, lightning. ->Man-made: Television screens.
Dimensional analysis (unit conversions)
- Take (enough) time to understand the question. Take a closer look at the unit for the unknown quantity! It helps you plan for the math setup. Always use the ABCsteps. - For conversion problems, never begin your calculation with a conversion factor (as it can be flipped if needed). - Always write the complete units while in your math setup. This will help you keep track of units and their cancellations. - Should memorize the following relationships (others will be provided): all the metric conversion prefixes (e.g. 1 km = 1000 m i.e. 10^3m, etc.), 1 inch = 2.54 cm (exactly), 1 kg = 2.2 lb (and 1 lb = 454 g), 1 mile = 1.6 km, 1 US gallon = 3.79 L, 1 cm^3 = 1 mL! - For every unit conversion problem, remember to do the SUN check (SFs, Unit(s), & Number) after you get the final answer.
Trend of atomic size when one moves down the group and across the period
- The atomic size (covalent radius) increases when one moves from top to bottom of a given group (because the electrons are added to additional shells). - The atomic size (radius) decreases when one moves from left to the right of a given period (because the effective nuclear charge increases, and electron cloud is strongly pulled by the nucleus).
Potential energy
- The energy an object has because of its relative position, composition, or condition. - Energy due to position or composition.
Kinetic energy
- The energy that an object possesses because of its motion. - Energy due to motion of the object and depends on the mass of the object and its velocity.
Molecular Orbital (MO) Configurations
- The number of molecular orbitals (MOs) formed is always equal to the number of atomic orbitals combined. - The more stable the bonding MO, the less stable the corresponding antibonding MO. - Lower energy orbitals are filled first. - Each MO can accommodate up to two electrons (with opposite spins). - Use Hund's rule when adding electrons to MOs of the same energy. - The number of electrons in the MOs is equal to the sum of all the electrons on the bonding atoms.
System
- The part of the universe we are interested in. - The system is usually defined as the substances involved in chemical and physical changes.
Surroundings
- The rest of the universe - All other matter, including components of the measurement apparatus, that serve to either provide heat to the system or absorb heat from the system.
Law of Conservation of Matter
- There is no detectable change in the total quantity of matter present when matter converts from one type to another. - This is true for both chemical and physical changes.
Hybridization in molecules containing multiple bonds (C2H4, C2H2, and CH2O)
- Valence bond theory and hybridization can be used to describe the bonding in molecules containing double and triple bonds. - The ethylene (C2H4) molecule has a double bond between two carbon atoms as indicated by the following Lewis structure: Each carbon has three electron groups: 2 single bonds 1 double bond
How to tell if an energy is absorbed, emitted if an electron moves from one energy level (n) to the other
- When electrons move from a lower energy level (ground state) to a higher energy level (excited state), they absorb the energy equal to the change in energy levels. - When electrons move from a higher to a lower energy level, they emit energy equal to the change in energy levels.
Gas Pressure (P)
- When gas particles strike the walls of their container, they exert pressure. - If the gas is heated, the molecules move faster and strike the walls of the container more often with increased force, increasing the pressure.
Vapor Pressure
- When liquid molecules with sufficient kinetic energy break away from the surface, they become gas particles or vapor. - In an open container, all the liquid will eventually evaporate. - In a closed container, the vapor accumulates and creates pressure called vapor pressure. - Each liquid exerts its own vapor pressure at a given temperature. - As temperature increases, more vapor forms, and vapor pressure increases.
Standard enthalpy of formation of an element in its most stable state is always...
- Zero - For example, O2(g), Ca(s), Hg(ℓ), etc.
SI units
- length (m) - volume (m3) - mass (kg) - time (s) - temperature (K)
Three kinds of information provided by every measurement:
- number - unit - uncertainty
Molecular orbitals have characteristics similar to atomic and hybrid orbitals
-Specific shapes and energies - Accommodate a maximum of 2 electrons each - Electron filling follows the Pauli exclusion principle - The number of molecular orbitals obtained equals the number of atomic orbitals combined
Measurement of Atmospheric Pressure
1 atm = 760 mmHg = 760 torr
The relationship between calories (cal), joules (J), and nutritional or dietary Calories (Cal)
1 cal = 4.184 J (1 calorie is worth many jewels!) 1 Cal = 1000 cal. 1 Cal = 1000 cal = 1 kilocal
1 cc = 1cm³
1 mL (exact)
Kinetic molecular theory of gases
1. Gases consist of molecules in constant, random motion. 2. Pressure arises from collisions with container walls. 3. No attractive or repulsive forces between molecules. Collisions elastic. 4. Volume of molecules is negligible. KE = (½)(mass)(velocity)^2 As T goes up, KE also increases - and so does velocity.
Density of water =
1.00 g/mL
1 mi (exact)
1.6 km
1 m
10 dm
1 g -> cg
100 cg
1 km
1000 m
1 L
1000 mL
kilo
10³
mega
10⁶
1 MW
10⁶ W
1 g -> μg
10⁶ μg
giga
10⁹
1 GHz
10⁹ Hz
1 s
10⁹ ns
centi
10⁻²
milli
10⁻³
deci
10⁻¹
micro
10⁻⁶
nano
10⁻⁹
Order of filling orbitals
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p....
1 kg (exact)
2.2 Ib
1 inch
2.54 cm (exactly)
Molar volume of any gas at STP
22.4 L/mol
When you convert the gram quantities into moles for empirical formula determinations, always have at least...
3-4 decimal places in the "mol"values.
1 US gallon (exact)
3.79 L
1 Ib (exact)
454 g
Rules for rounding ("5 or above" and "below 5" rules!)
5 or above - round up (add 1 to the digit)! below 5 -round down (retain the digit)!
1 mole of substance =
6.022 × 10²³ particles (Avogadro's number)
When is Mole Day celebrated annually?
6:02 am to 6:02 pm 10/23 (Oct 23rd).
Electron configuration for cations (positively charged ions) and anions (negatively charged ions).
A cation (positively charged ion) forms when one or more electrons are removed from an atom. For main group elements, the electrons that were added last are the first electrons removed. For transition metals and inner transition metals, the highest ns electrons are lost first, and then the (n - 1)d or (n - 2)f electrons are removed. A anion (negatively charged ion) forms when one or more electrons are added to a parent atom. The electrons are added in the order predicted by the Aufbau principle. When electron(s) is/are removed from an atom, they are removed from the outermost shell!
Molecular orbital diagram
A depiction of the relative energy and number of electrons in each MO, as well as the atomic orbitals from which the MOs form.
Theory
A model that describes how the observations occur using experimental results.
Assign and/or count sigma (σ) and pi (π) bonds in a given molecule
A single covalent bond is always a sigma bond, a double bond has a sigma and a pi bond, and a triple bond has a sigma and two pi bonds.
Hypothesis
A statement that explains the observations.
Two ways of preparing solutions with molarity concentrations
A) By dissolving certain mass (we can always calculate moles!) in solvent to make a certain volume of solution. B) Using dilutions.
Law of definite proportions or constant composition
All samples of a pure compound contain the same elements in the same proportion by mass.
Closed system
Allows the transfer of energy but not mass.
Microscopic
Almost always visited in the imagination. Micro also comes from Greek and means "small." Some aspects of the microscopic domains are visible through a microscope.
Line spectrum of hydrogen atoms (why are only 4 lines visible?)
Although hydrogen has only one electron, it contains many energy levels. When its electron jumps from higher energy level to a lower one, it releases a photon. Those photons cause different colours of light of different wavelengths due to the different levels. Those photons appear as lines. For this reason, though hydrogen has only one electron, more than one emission line is observed in its spectrum.
Tip:
Always finish unit cancellations in one single step (a ×𝐛/𝐚 ×𝐜/𝐛×......). Do write complete units (e.g. moles CH4 instead of just "moles") throughout the calculation steps so that you can check which unit is canceled and which is not. Don't forget to do the SUN (Sig. figs., Unit(s) & Number) check at the end of every calculation!
Accuracy
An accurate measurement that is very close to the right (or accepted) value. Requires only one measurement. accurate = accuRIGHT
Octect rule
An octet - Is 8 valence electrons - Is associated with the stability of the noble gases - Does not occur with H and He, which are stable with two valence electrons (duet or duplet).
Oxidizing and Reducing Agent
An oxidizing agent is reduced, and a reducing agent is oxidized. Draw the redox triangle to confirm. It is the "deal" of electron(s)
You should be able to find out the charge on a metal ion (cation) by using the periodic table or Roman numeral. The polyatomic ions you need to know are:
Anions ending with -ate ("Nick the Camel ate Clam Supper in Phoenix"), with -ite ("ite" is "lite" i.e. one O less than that of "-ate"), NH4+ (the unique one -the "talking cat") i.e. ammonium, C2H3O2-or CH3COO- (acetate), CN- (CyaNide), and OH- (HydrOxide).
Remember: the lone pairs on the terminal atoms (side atoms) do NOT have...
Any role in determining electron group and molecular geometry. For example: in CCl4, the number of electron groups we care = 4 (around the central atom C only).
Matter
Anything that has mass and occupies space. The material of which things are made. Matter has.. - Mass - Volume (i.e. occupies space) Examples of matter: Wood, sand, people, water, and air are all examples of matter. Light is not matter; it is a form of energy.
Quantitative properties
Are measured and expressed with a number. Examples: 15 inches, 25 seconds, 42 grams, etc.
Applications of sig. figs. concepts in our daily lives.
Areas of life where we are measuring things to a certain level of accuracy.
Pressure and Volume Relationship
As pressure increases, volume decreases.
Temperature and Volume Relationship
As temperature increases, volume increases.
Rules for counting Scientific notation: Zeros may create problems: Always use the Atlantic-Pacific mnemonic device.
Ask yourself a question: "Is decimal PRESENT or ABSENT in the number provided?" decimal PRESENT - start from the Pacific side decimal ABSENT - start from the Atlantic side
Charles's Law
At constant pressure, the volume of a fixed amount of gas is directly proportional to its Kelvin temperature. V/T = Constant V1/T1 = V2/T2
Avogadro's Law
At constant temperature and pressure, the volume of a sample of gasis directly proportional to the number of moles in the sample. V/n = Constant V1/n1 = V2/n2
Gay-Lussac's Law
At constant volume, the pressure exerted by a fixed amount of gas is directly proportional to its Kelvin temperature. P/T = Constant P1/T1 = P2/T2
Molecule
At least two or more atoms (of same or different elements) bound together. Ex. O2 molecule (two O atoms), H2O molecule (two H and one O atoms)
Mass of an atom: Why is the AMU scale needed?
Atomic Mass Unit (AMU) is defined as precisely 1/12 the mass of an atom of carbon-12. The carbon-12 (C-12) atom has six protons and six neutrons in its nucleus. In imprecise terms, one AMU is the average of the proton rest mass and the neutron rest mass. AMU is used to express the relative masses of, and thereby differentiate between, various isotopes of elements.
Diamagnetism
Atoms are not attracted to a magnetic field, but rather are slightly repelled.
Velocity of Gas Molecules
Average velocity decreases with increasing mass.
Why is molarity so useful?
Because it directly compares the "moles" of solute with volume of solution in liters. If molarity is given in the question, always think that you could get conversion factors from molarity information. For example, 0.250 M NaCl means that 0.250 mol NaCl is present in 1 L NaCl solution. You can get two conversion factors from this. 𝟎.𝟐𝟓𝟎 𝐦𝐨𝐥 𝐍𝐚𝐂𝐥/ 𝐋 𝐍𝐚𝐂𝐥 𝐬𝐨𝐥𝐮𝐭𝐢𝐨𝐧 and 𝐋 𝐍𝐚𝐂𝐥 𝐬𝐨𝐥𝐮𝐭𝐢𝐨𝐧/ 𝟎.𝟐𝟓𝟎 𝐦𝐨𝐥 𝐍𝐚𝐂𝐥 (the choice of the conversion factor totally depends on your question-you cannot decide now!)
Open system
Can exchange mass and energy with the surroundings.
In ions, # of p+≠ # of e-. There are two types of ions: cations and anions.
Cations are +ve (Cations are pawsitive ) Anions are negative
Periodic trend for the number of valence electrons along the group
Check the group #
The total energy content of the universe is...
Constant
Symbolic domains
Contains the specialized language used to represent components of the macroscopic and microscopic domains, such as chemical symbols.
Sig. fig. rules for addition/subtraction
Count the decimal places!
Sig. fig. rules for multiplication/division
Count the total # of sig. figs.!
Predicting the type of hybridization (sp, sp2, sp3, sp3d, and sp3d2) based on the Lewis structure of the given molecule by
Counting the electron groups (clouds) around the central atom!
A polar bond is a
Covalent bond with greater electron density around one of the two atoms.
Electron configuration of Cr and Cu
Cr has 24 e-s to place: Expected electron configuration = 1s2^2s^22p^63s^23p^64s^23d^4 Actual electron configuration = 1s^22s^22p^63s^23p^64s^13d^5 Cu has 29 e-s to place: Expected electron configuration = 1s^22s^22p^63s^23p^64s^23d^9 Actual electron configuration = 1s^22s^22p^63s^23p^64s^13d^10 Explanation: The half-filled and completely filled subshells have extra stability!
Dilution Formula
C₁•V₁= C₂•V₂ C₁ and V₁ are initial concentration and volume (before dilution) and C₂ and V₂ are final concentration and volume (after dilution).
Trend of ionization energy
Decreases down a group (easier to remove electrons as you go down), increases across a period from left to right (harder to remove electrons as you move right).
Extensive property
Depends on the amount of matter present. Examples: mass, volume, heat
Molecular geometry
Describes the arrangement of atoms, excluding lone pairs.
Electron group geometry
Describes the arrangement of electron groups.
Always keep a few extra...
Digits in every step of calculations and do the rounding in the final step. For example, after getting the final answer. This helps to minimize the "rounding errors".
Quantized
Discrete (individually distinct) energy levels
Exact numbers
Do not involve rounding and that's why they have no uncertainty. Ex. 7 cars, 3 apples, 1 min = 60 s, 1 ft = 12 in, 1 in = 2.54 cm.
Qualitative properties
Do not require measurement and are usually based on observation. Examples: red, thick, heavy, etc.
Isolated system
Does not exchange either mass or energy with its surroundings.
According to molecular orbital theory..
During bond formation, the atomic orbitals combine to form new orbitals known as molecular orbitals.
Determining if a bond is polar covalent, non-polar covalent, or an ionic bond
EN difference = 0 to 0.4 (non-polar covalent) EN difference = 0.5 to 1.8 (polar covalent) EN difference > 1.8 = ionic
Bond breaking is an
Endothermic process
Exact numbers and sig. figs
Exact numbers do not limit sig. figs. in calculations as they do not involve rounding and have no uncertainty!
Homogenous Mixtures
Exhibits a uniform composition and appears visually the same throughout. Another name for a homogenous mixture is a solution. Its composition can be same throughout because it may be prepared from same amounts.
Bond making is an
Exothermic process
Observations
Facts obtained by observing and measuring events in nature.
Fast and Slow movement of molecules
Fast moving molecules → High thermal energy →"Hot"• Slow moving molecules → Low thermal energy→"Cold"
The basic features of a symbol for an element:
First letter capital and second letter (if the symbol has one) lowercase.
Visualizing an atom:
Football stadium (atom) vs blueberry (nucleus) example.
Should be able to figure out the number of valence shell electrons (VSE) from the group number
For example, C is in group 14 (4A) VSE. = 4 Br is in group 17 (7A) VSE = 7
Be able to determine the formal charge of atom in a given species and indicate the most plausible Lewis structure based on the...
Formal charge concept (FC = "Valence e-s" -"Assigned or Owned e-s" or simply "Should Have" -"Does Have").
Octet state can be achieved b
Gaining, losing or sharing electrons.
The general behavior of gases
Gas particles move in random, straight-line motion. Gas particles possess a greater kinetic energy than the particles of a liquid or solid. As temperature increases, particles move faster and, thus, have greater kinetic energy. The particles of a gas have minimal interactions, except collisions with each other. Density - As pressure increases, density also increases. Compressibility -
Real gases
Gases are closest to IDEAL at low pressures and high temperatures.
Mnemonic for metric prefixes
Great Mighty king Bill diligently checks millipede w/ microscope @ noon!
Columns on the periodic table are called
Groups
Seven elements that exist in diatomic form
H, N, O, F, Cl, Br, I Mnemonic: I Brought Clay For Our New House Example: if the question says "Oxygen gas reacts with ......" You must write O₂ (g) in the equation, not O (g).
Heterogeneous Mixtures
Has a composition that varies from point to point. Its composition can vary because it may be prepared from varying amounts
Measured numbers
Have uncertainties as they do involve rounding. The uncertainty is on the last digit. Examples: mass of a lab sample = 4.60 g, length of a rope = 12 ft.
Sign convention for heat (q) and work (w).
Heat IN to the system (enters as reactant) →+q (endothermic) Heat OUT of the system (exits as product) → -q (exothermic). Work ON the system → +w; work BY the system → -w.
Enthalpy (H) =
Heat content at constant pressure (qp).
An antibonding molecular orbital has
Higher energy and lower stability than the atomic orbitals from which it was formed.
Precision
How close various sets of measurements are to one another. (= how repeatable or reproducible the data points are) Requires multiple measurements. PREcise = REpeatable
Law of conservation of matter
If atoms are neither created nor destroyed during a chemical change, then the total mass of matter present when matter changes from one type to another will remain constant.
What do positive and negative power of 10 mean?
If the original number is greater than 1, n is positive. If the original number is smaller than 1, n is negative.
Combustion Reaction
In a combustion reaction, the reducing agent is called the fuel. The oxidizing agent is usually O₂. When compounds composed of just carbon and hydrogen undergo combustion, CO₂ and H₂O are products. Heat and light are also often produced.
Single-Displacement Reaction
In one type of single replacement reaction, an ion in solution is often displaced or replaced via an oxidation reduction reaction, or a redox reaction.
Intensive property
Independent of the amount of matter present. Examples: density, temperature **INTENSIVE property is INDEPENDENT of the sample size!**
Molecular Formula
Indicates the actual numbers of atoms of each element in a molecule of the compound.
Empirical Formula
Indicates the simplest whole-number ratio of the number of atoms (or ions) in the compound.
Ionic bond
Involves complete transfer of one or more electrons from one atom to another. Example: NaCl, LiBr, etc. Na+ + Cl- → NaCl
Chemical change
Involves the change in chemical composition of matter. Examples: rusting, digestion of food.
Covalent bond
Involves the sharing of valence electrons between combining atoms. Example: Cl2, HCl, etc.
Physical Change
Is a change in the state or properties of matter without any accompanying change in its chemical composition. Examples: changes of state (melting, freezing, condensation)
Temperature
Is a quantitative measure of "hot" or "cold"
Thermal energy (heat)
Is a type of kinetic energy (KE) associated with the random motion of atoms and molecules.
Standard enthalpy of formation (ΔH°F)
Is an enthalpy change for a reaction in which exactly 1 mole of a pure substance is formed from its constituent free elements in their most stable states under standard state conditions.
Wave
Is an oscillation or periodic movement that can transport energy from one point in space to another.
Bonding pairs (shared pairs)
Is composed of two electrons that are in a bond.
Lone pairs
Is composed of two electrons that are not in a bond.
Mixture
Is composed of two or more types of matter that can be present in varying amounts and can be separated by physical changes. Evaporation is an example of a physical change. There are two types of mixtures: homogenous mixtures and heterogeneous mixtures.
Electron affinity
Is the change in energy (in kJ/mole) of a neutral atom (in the gaseous phase) when an electron is added to the atom to form a negative ion.
Wavelength (λ; pronounced as "lambda")
Is the distance between identical points on successive waves.
Standard enthalpy of combustion (ΔH°C)
Is the enthalpy change when exactly 1 mole of a substance burns (combines vigorously with oxygen) under standard state conditions.
Gas Diffusion
Is the gradual mixing of molecules of one gas with molecules of another by virtue of their kinetic properties.
Ionization energy
Is the minimum energy (kJ/mol) required to remove an electron from a gaseous atom in its ground state.
Frequency (v; pronounces as "nu")
Is the number of successive wavelengths that pass a given point in a unit time.
Gas Effusion
Is the process by which gas under pressure escapes from one compartment of a container to another by passing through a small opening.
Amplitude
Is the vertical distance from the midline of a wave to the peak or trough (or simply the height of the wave).
Heisenberg Uncertainty Principle
It is fundamentally impossible to determine simultaneously and exactly both the momentum and the position of a particle.
Law of Conservation of Mass
It is so important to balance every single equation.
Macroscopic
It is the realm of everyday things that are large enough to be sensed directly by human sight or touch.
What is the "mole" quantity?
It's just like dozen! 1 dozen of any sample has 12 items, but 1 mole of any sample has 6.02 ×10^23 items! The mole unit is also written in its abbreviated form "mol".
Temperature units interconversion: °C to °F (and vice-versa) and °C to K (and vice-versa)
K = (°C + 273.15) °F = (°C × 𝟗/𝟓) + 32 °F = (°C × 1.8) + 32
Temperatures should ALWAYS be expressed in
Kelvin
A bonding molecular orbital has
Lower energy and greater stability than the atomic orbitals from which it was formed.
Electron group (cloud) geometry
Make sure to count the electron groups around the central atom. Check the formula type ABE (B + E = no. of electron clouds; B = determined by the # of side atoms attached to the central atom and E = # of lone pair(s) on central atom). You must draw the Lewis dot structure for the given species to be able to determine the number of electron groups (clouds). For example, for H2O, there are two H atoms bonded to central atom O and there are two lone pair of electrons on central atom. Therefore, # of electron clouds in H2O = B+ E= 2 + 2 = 4.
Seven elements in the periodic table existing in the diatomic form:
Mnemonic: I Brought Clay For Our New House! I, Br, Cl, F, O, N, H
Molarity Formula:
Molarity (M) = 𝐦𝐨𝐥𝐞𝐬 𝐨𝐟 𝐬𝐨𝐥𝐮𝐭𝐞 (𝐦𝐨𝐥)/𝐯𝐨𝐥𝐮𝐦𝐞 𝐨𝐟 𝐬𝐨𝐥𝐮𝐭𝐢𝐨𝐧 (𝐋)
Molarity (M)
Molarity is the ratio of moles of solute to the volume of solution in liters, hence mol/L.
Mole fraction and partial pressures
Mole fraction = moles of given gas/ total moles in the gas mixture Partial pressure of a gas = mole fraction × total pressure of the gas mixture.
Molecular geometry (shape)
Molecular geometry depends on the number of atoms bonded (we ignore the lone pair(s) for determining molecular shape. For example, the electron group geometry is tetrahedral (4 electron groups) but the molecular shape is bent (ignore the lone pairs on O atom)
Nomenclature (names and formulas) of hydrates and acids. Mnemonic device for acid naming:
My ride has hydrolic. I ate something icky. Sprite is delicious.
Pauli exclusion principle
No more than two e-s occupy each orbital and the two e-s must have opposite spins (represented by up and down arrows).
Atomic number =
Number of protons *Used to determine the number of neutrons and electrons.*
The coefficients in a balanced chemical equation always indicate...
Numbers (individual particles or "moles"), not "mass", of each reactant or product!!
Decomposition Reaction
Occurs when a substance is broken down into small chemical units.
Reaction products of a neutralization reactions
One of the products is H₂O (l)! Use the charge balance to get the correct formula.
Redox reaction
Oxidation and reduction always occur simultaneously. One species is oxidized and the other one is reduced. Redox (oxidation-reduction) reactions are electron transfer reactions. Must know which species is oxidized and which one is reduced in a given redox pair. OIL RIG Do not guess! Use the principles!!
Combined Gas Law
P1V1/n1T1 = P2V2/n2T2
Should be able to determine the relative (average) atomic mass of the element when the individual atomic masses and percent natural abundances of different isotopes are provided by using this formula...
PAAM Sum Formula! Sum of the product of Percent Abundance and Atomic Mass of each isotope.
Ideal gas law
PV = nRT The value of R= 0.0821 L.atm/(mol.K)
Why is molecular orbital theory (MOT) needed?
Paramagnetic behavior of oxygen, O2
Formula for % yield.
Percent yield = actual yield (g)/ theoretical yield(g) × 100%. The percent yield can never be higher than 100%!
While determining the empirical formula from a given set of data, always use the following conversion steps:
Percent → Grams → Mol→ Simplest Whole Numbers (Mnemonic: Proud Grey Mole Shows Weird Nose"). Empirical formulas always have whole numbers as subscripts representing the moles of each atom!
Rows on the periodic table are called
Periods
Three special reaction types
Precipitation Redox (oxidation-reduction) Acid-base (neutralization) reactions.
Pressure
Pressure (P) is the amount of force applied per unit area: Pressure (P) = force/area We can describe the pressure exerted by gas particles by: Pressure (P) = area of gas particles/area of container
Experiments
Procedures that test the hypothesis.
Compounds
Pure substances that can be broken down into simpler substances by chemical changes. Consist of two or more types of elements chemically bonded. -> Examples: H2O, C6H12O6, NaCl -> The properties of compounds are different from the uncombined elements making up the compound.
Elements
Pure substances that cannot be broken down into simpler substances by chemical changes. The known elements are displayed in the periodic table. - There are 118 known elements. - Ninety of these occur naturally. - Two dozen or so have been created in laboratories. Pure substances consist of one type of element -> Examples: Gold (Au), Phosphorus (P), Argon (Ar)
Identify if the given sample will sink or float when placed in water
Sample with a density greater than 1.00 g/mL will sink and that with a density lower than 1.00 g/mL will float.
If a number is expressed as a scientific notation, all the digits on the coefficient are...
Significant (you can still double check with Atlantic-Pacific mnemonic device).
Elements from the same group have...
Similar properties
Atom
Smallest unit of an element. Ex: an atom of gold, an atom of copper. Atoms are represented with elemental symbols.
Non-quantized
Smooth transition between levels.
Symbols used in writing chemical equations
Solid = (s) Liquid = (l) Gas = (g) Aqueous = (aq) In aqueous solutions, the solvent is always water. The delta(∆) symbol above the arrow (∆→) means that reactants are heated.
Mnemonic device for Sig Figs in Calculations
Some Fish May Die Due to Pollution And Suffocation (SFs for x & ÷ and Decimal Places + & -).
Aufbau (Building up) Principle
States that each electron occupies the lowest energy orbital available.
Law of multiple proportions
States that when two elements react to form more than one compound, a fixed mass of one element will react with masses of the other element in a ratio of small, whole numbers.
Mass to number of particles or vice-versa involves two conversion factors (follow the roadmap provided).
Summary: Every mole conversion problem involves "mol" unit. If the question does not involve "mol" you have to use one of the two conversion factors to get "mol" and then use second conversion factor to get your target unit! In case you are confused, look for "moles". ☺
Universe
System + Surroundings
STP conditions
T = 0°C (= 273.15K) and P = 1 atm
ΔT =
T final - T initial
Electron configuration
The arrangement of electrons in an atom
Chemical property
The change of one type of matter into another type (or the inability to change) Examples: flammability, toxicity, acidity, reactivity, and heat of combustion.
Properties
The characteristics that enable us to distinguish one substance from another.
Chemical Combination
The chemical combination of two or more elements in a fixed proportion results in the formation of a compound. For example, both hydrogen and oxygen are elements but water (H2O) is a compound.
Choose appropriate conversion factor(s) based on the information given in the question.
The choice of your conversion factor depends upon "which unit you're trying to cancel" and/or "which unit you're trying to get".
Abbreviated (condensed) electron configuration
The condensed electron configuration includes the symbol for the nearest, smaller noble gas in square brackets and then the symbols for occupied orbitals that contain valence electrons.
Why is density an intensive property although mass and volume are extensive properties?
The density of the system remains unchanged even when it is divided into two parts. That means density is independent of the mass or the extent of the system. Thus, it is an intensive property.
Electromagnetic Spectrum
The electromagnetic spectrum is an arrangement of different types of radiation from the longest to the shortest wavelength.
Double-Displacement Reaction
The ions from one reactant swap places with the ions from the other reactant; one of the products is insoluble.
Since uncertainty is the part of a measurement...
The last estimated digits is also a part of significant figures (sig. figs. or SFs).
Hund's rule
The lowest-energy configuration for an atom with electrons within a set of degenerate orbitals is that having the maximum number of unpaired electrons or parallel spins. (Orbitals within the same subshell have the same energy and are said to be degenerate orbitals).
The zig-zag line on the periodic table separates
The metals from non-metals. The elements to the left side (except for H) are metals and form cations during chemical reactions. The elements to the right are non-metals and form anions during chemical reactions (except for group 18 or noble gases which are chemically inert.)
Scientific Method
The path of discovery that leads from question and observation to law or hypothesis to theory, combined with experimental verification of the hypothesis and any necessary modification of the theory.
Boyle's Law
The pressure of a fixed amount of gas at a constant temperature is inversely proportional to the volume of the gas. P ×V = Constant P1 * V1 = P2 * V2
Limiting reactant
The reactant that is completely used up in a chemical reaction and produces smaller number of moles of product(s) is called the limiting reactant (or limiting reagent) because it limits the amount of product that can be formed.
Chemistry
The study of the composition, structure, and properties of matter and of changes that occur in matter.
Thermochemistry
The study of the heat absorbed or released during chemical and physical changes.
Products
The substances generated by the reaction
Reactants
The substances undergoing a reaction
Internal energy
The total of all possible kinds of energy present in a substance. E or U = kinetic energy + potential energy
All the atoms are electrically neutral unless...
They undergo chemical reactions and form ions. In atoms, # of p+ = # of e-. The number of protons remains always the same!
Mole fraction
Total mole fraction is a fraction and has no unit. The total of all mole fractions is always 1.
Equality
Two equivalent quantities with different units. Ex: the price of 1 lb tomatoes in a grocery store is $1.58. - Conversion factors and equalities: every equality gives two conversion factors! - Any quantity with two units in a ratio can give two conversion factors. -> For example: density (g/mL), dose (mg/kg of body weight), speed (mi/h), etc. - Percentage (%) information can be used as a conversion factor.
Calculation based on stoichiometry
Use the "Mole Conversion Roadmap" Make sure to write full (or complete) units in calculation steps.This helps remove ambiguity! Almost every stoichiometry problem involves "moles" in the conversion factors. Follow the "moles"!
Valence Bond Theory Limitations
Valence bond theory must be modified to explain the covalent bonds formed in other molecules.
VSEPR Theory
Valence-shell electron-pair repulsion theory; because electron pairs repel, molecules adjust their shapes so that valence electron pairs are as far apart as possible.
Comparison of the size of an atom with its ion
Visualize the change in the size of electron cloud when electrons are added or removed.
Altitude and Atmospheric Pressure Relationship
When altitude increases, the atmospheric pressure decreases.
Combination Reaction
When two or more chemical species react and form bonds.
ΔT positive or negative
When ΔT = negative, q becomes negative (exothermic process) When ΔT = positive, q becomes positive (endothermic process).
Rules for assigning oxidation numbers (O. N.)
You can use Oxidation Number as a reference! Don't get confused - it is NOT always the charge from periodic table group numbers! For example, in an ionic compound oxygen forms oxide ion by gaining two electrons hence O₂-but the oxidation number for O is NOT always ₂-. In H₂O₂,O. N. for oxygen is -1, in potassium peroxide (KO₂), O. N. for oxygen is -½ and O. N. for oxygen in O₂ molecule is 0.
Precipitation reactions
You should be able to - a) Predict the correct formulas of products using "Split, Swap & Balance" approach, make sure to check all the atoms and charges are balanced (check the charge ratios) and identify the precipitate(s) and aqueous (aq) phases (solubility rules table will be provided). b) Write down complete ionic equation (ONLY the ionic compounds in aqueous phase (aq) are ionizable!)using molecular equation (balanced chemical equation). Make sure you balance the charges. c) Identify the spectator ions (common ions present in both reactant and product side) d) Write down net ionic equation. Make sure all the atoms and charges are balanced on both sides of equation. e) Visualize the process using the online simulation for precipitation reactions (simply click on the link provided in lecture handouts).
Symmetrical molecules usually have...
Zero dipole moment (since polarities cancel). Use the SNAP rule. Symmetrical = Nonpolar Asymmetrical = Polar
Molarity(M) =
a unit to represent the concentration of a solution.
You should be able to determine
a) the limiting reactant b) theoretical yield (in mol and/or grams) of product(s) c) percent yield d) the amount of excess reagent left.
Strong Acids
acids that completely react in this fashion
The average atomic masses of the ions can be approximated to be the same as the...
average atomic masses of the neutral atoms.
Wave equation
c = λ × ν The value for speed of light (c) = 3.00 ×108m/s).
Trend of electron affinity
decreases down a group, increases across a period
Ionic substances are composed of...
discrete cations and anions combined in ratios to yield electrically neutral bulk matter.
Covalent substances exist as...
discrete molecules
Determine the bond order from the MO diagram.
formula: bond order = 𝐁𝐌𝐎e-𝐬 − 𝐀𝐁𝐌𝐎e-𝐬/𝟐
Neutralization reaction
is a specific type of acid-base reaction in which the reactants are an acid and a base, the products are often a salt and water, and neither reactant is the water itself.
Acids
is a substance that will dissolve in water to yield hydronium ions, H₃O+.
Base
is a substance that will dissolve in water to yield hydroxide ions, OH−.
The mole (mol)
is the amount of a substance that contains as many elementary entities as there are atoms in exactly 12.00 grams of C-12 isotope.
Density
mass/volume
What are the three classes of elements called?
metals, nonmetals & metalloids.
The formula mass for an ionic compound may not correctly be referred to as a...
molecular mass
The formula mass of a covalent substance may be correctly referred to as a...
molecular mass
Nonmetals only =
molecular; di-, tri-, Prefixes in the name = Molecular!
Ionic compounds do not exist as...
molecules
Meaning and symbols for all 4 quantum numbers
n = principal quantum number (represents the size and energy of the electron cloud) ℓ = angular momentum quantum number (represents the shape of the electron cloud) mℓ = magnetic quantum number (represents the orientation of the electron cloud along various axes) ms = spin quantum number (represents the electron spin)
2p orbital
n= 2, ℓ = 1 (ℓ= 0 represents s, ℓ= 1 represents p, ℓ= 2 represents d, and ℓ= 3 represents f orbital) mℓ= +1, 0, and -1. Therefore, p orbital has 3 orientations along x-, y- and z-axes. The value of spin quantum number is always +½ or -½ (representing clockwise and anticlockwise spin).
Problems related to ppm and ppb
ppm = mass of solute/ mass of solution × 10⁶ and ppb = mass of solute/ mass of solution × 10⁹ ppm is represented as mg/kg ppb as mcg/kg.
The quantity of heat released or absorbed
q= c× m× ΔT Where q= quantity of heat absorbed (+) or released (-) m= mass of the substance c= specific heat ΔT = change in temperature (T final-T initial). The specific heat of water (𝑐H2O) = 1 cal/(g•°C) or 4.184 J/g•°C.
Solution =
solute + solvent (Solute is present in smaller amount and solvent is present in larger amount. In aqueous solutions, water = solvent and the things which get dissolved (say table salt, sugar, CaCl2, etc.)= solute)
The formulas mass of a substance is the...
sum of the average atomic masses of all the atoms in the substance's formula.
Empirical formula =
the simplest whole number mole ratio of combining elements (atoms).
Reaction stoichiometry
the stoichiometry concept is very similar to a recipe to make sandwiches. Make sure you can generate the conversion factors using mole ratios (mole-mole factors) from a balanced chemical equation (recipe).
Calculate bond enthalpy change for a chemical reaction
ΔH° = [Energy used for Bond Breaking (BB)] -[Energy released after Bond Making (BM)]
Enthalpy (H)
ΔU = q + w q = quantity of heat involved w = the P - V work done by the gas
Arrows in Reactions
→ = complete dissociation = strong acid/base, ⇌ = partial dissociation = weak acid/base.
Equation based on enthalpy and First law of thermodynamics:
∆𝐻 = ∆𝑈 + 𝑃∆𝑉
Standard enthalpy (Direct method)
∆𝑯𝐫𝐱𝐧𝐨 = Total ∆𝑯𝐟𝒐(products) -Total ∆𝑯𝐟𝒐(reactants).