Chem/Phys Flashcards
Atomic Weight
The weighted average of the masses of the naturally occurring isotopes of an element, in amu per molecule or grams per mole
Mole
A unit used to count particles; represented by Avogadro’s number 6.022 x 10^23 particles
mass of sample/molar mass
Also the amount of substance that contains the same number of particles as a 12.00g sample of C12.
Isotopes
For a given element, multiple species of atoms with the same number of protons but different numbers of neutrons
Planck’s quantum theory
Energy emitted as electro-magnetic radiation from matter exists in discrete bundles called quanta
Bohr’s Model of H Atom
Energy of electron = E = (2.18 * 10^-18 J/e-)/n^2
EM energy of photons = E = hc/wavelength
(h = 6.626 x 10^-34 J/s)
Balmer series vs Lyman series
Group of hydrogen emission lines corresponding to transitions from upper levels n > 2 VS Group of hydrogen emission lines corresponding to upper levels n > 1 to n = 1
Absorption spectra
Characteristic energy bands where electrons absorb energy
Heisenberg Uncertainty Principle
Impossible to know the location and momentum of an electron at the same time
Quantum numbers
Principle (n) - the larger the integer value, the higher the energy level and radius of the electrons orbit; max # e- in energy level n = 2n^2
Azimuthal (l) - Subshells; four, corresponding to I = 0,1,2,3 are s, p, d, f; max # e- within subshell = 4l + 2
Magnetic (ml) - orbital within a subshell where highly likely to find electron; between 1 and -1
Spin (ms) - spin of a particle or intrinsic angular momentum; +1/2 or -1/2
Hund’s Rule
Within a given subshell, orbitals are filled such that there are a maximum number of half filled orbitals with parallel spins
Valence electrons
Electrons of an atom that are in its outer energy shell and available for bonding
Coordination Compounds
Lewis acid-base adduct with a cation bonded to at least one electron pair donor (including H2O); Donor molecules are called ligands and use coordinate covalent bonds.
Chelation
When the central cation in a coordination compound is bound to the same ligand multiple times
Hydrogen bonding
The partial positive charge of the hydrogen atom interacts with the partial negative charge located on the electronegative atoms (F, O, N) of nearby molecules
Dipole-dipole Interactions
Polar molecules orient themselves such that the positive region of one molecule is close to the negative region of another molecule.
Dispersion forces
The bonding electrons in covalent bonds may appear to be equally shared, but at any particular point in time they will be located randomly throughout the orbital, permitting the unequal sharing of electrons and leading to transient polarization and counterpolarization of the electron clouds of neighboring molecules
Units for rate constant?
zero-order - M/s
first-order - s^-1
second-order - M^-1s^-1
third-order - M^-2s^-1
Combustion reaction
A fuel, such as a hydrocarbon, is reacted with an oxidant, such as oxygen, to produce an oxide and water
Combination reaction
Two or more reactants form one product
Decomposition reaction
A compound breaks down into two or more substances, usually as a result of heating or electrolysis
Single-displacement reaction
An atom (or ion) of one compound is replaced by an atom of another element
Double displacement reaction
Also called metathesis reactions; elements from two different compounds displace each other to form two new compounds
Net ionic equation
Written showing only species that actually participate in the reaction
Neutralization reaction
A specific type of double-displacement reaction that occurs when an acid reacts with a base to produce a solution of a salt and usually water
Factors that affect reaction rates?
Reactant concentrations, temperature, medium, catalysts
Law of Mass Action
aA + bB –> cC + dD
Keq = [C]^c[D]^d/[A]^a[B]^b
Properties of equilibrium constant
Pure solids and liquids don’t appear in the expression
If Keq»_space; 1, little of the reactants compared to the products.
If Keq «_space;1, little of the products
compared to the reactants.
If Keq is close to 1, approximately equal amounts of the two
Le Chatelier’s Principle
Used to determine the direction of the reaction at equilibrium when subjected to stress (ie. change in concentrations, pressure, volume, or temp)
Isolated vs closed vs open systems
Isolated - no exchange of energy or matter
Closed - no exchange of matter but exchange of energy
Open - exchange of matter and energy
Isothermal Process
Constant temperature; ∆U = 0; first law is Q = W
Adiabatic process
Constant heat; Q = 0, first law is ∆U = -W
Isobaric process
Constant pressure
Isovolumetric (Isochoric) process
Constant volume; W = Q, first law is ∆U = Q
Endothermic vs Exothermic
Absorb energy (positive ∆H) vs Release energy (negative ∆H)
Heat absorbed or released in a given process
q = mc∆T (c - specific heat)
State functions
Describe the macroscopic properties of the system; pressure, density, temperature, volume, enthalpy, internal energy, free energy, and entropy
Enthalpy
Used to express heat changes at constant pressure
Standard heat of formation
The enthalpy change that would occur if one mole of a compound was formed directly from its elements in their standard states
Standard heat of reaction
the hypothetical enthalpy change that would occur if the reaction were carried out under standard conditions
Hess’s Law
the enthalpies of reactions are additive; the reverse of any reaction has the same magnitude with opposite sign
Bond dissociation energy
The average energy required to break a particular type of bond in one mole of gaseous molecules
Bond enthalpy
The standard heat of reaction can be calculated using the values of bond dissociation energies of particular bonds
Entropy
The measure of the distribution of energy (“randomness”) throughout a system
Reaction spontaneity by ∆H and ∆S signs
-/+ : spont at all temps
+/- : nonspont at all temps
+/+ : spont at high temps
-/- : spont at low temps
Reaction quotient
Once a reaction commences, the standard state conditions no longer hold; Q is the same equation as K
Pressure Equivalents
1 atm = 760 torr = 760 mmHg = 101,325 Pa
STP vs Standard Conditions
STP - 0˚C, 1 atm; used for gas law calculations
Standard conditions - 25˚C, 1 atm, 1 M concentrations; used for standard enthalpy, entropy, free energy, or emf
Boyle’s Law
P1V1 = P2V2
Charle’s Law
V1/T1 = V2/T2
Gay Lussac’s Law
P1/T1 = P2/T2
When do ideal gases behave unideally?
Small volume; high pressure or low temperature
Van der Waals equation of state
accounts for deviations from ideality that occur
(P + n^2a/V^2)(V-nb) = nRT
1 mol of Gas at STP is how many liters?
22.4
Dalton’s law of partial pressures
The total pressure of a gaseous mixture is equal to the sum of the partial pressures of the individual components
Calculate partial pressure of a gas
Pgas = Xgas*Ptotal
Kinetic molecular theory of gases
An explanation of gaseous molecular behavior based on the motion of individual molecules
Average molecular speeds
K = 1/2mv^2 = 3/2kBT
Root-mean-square speed
urms = √3RT/M
Colligative properties
Properties derived solely from the number of particles present, not the nature of the particles
Freezing point depression
∆Tf = iKfm (m is molality)
Boiling point elevation
∆Tb = iKbm (m is molality)
Osmotic pressure
π = MRT
Raoult’s Law
vapor pressure lowering; the partial vapor pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiplied by its mole fraction in the mixture
Pa = XaP˚A; Pb = XbP˚b
Graham’s law of diffusion and effusion
Diffusion - occurs when gas molecules distribute through a volume by random motion
Effusion - occurs when gas flows under pressure from one compartment to another through a small opening
r1/r2 = 1√M1/M2
Solubility rules
1) All group 1 salts or ammonium cations are water sol.
2) All salts with nitrate (NO3-) or acetate anions are water sol.
3) All chlorides, bromides, and iodides are water soluble, except Ag+, Pb+ and Hg2+
4) All sulfate ion salts (SO42-) are water soluble, except Ca2+, Sr2+, Ba2+, and Pb2+
5) All metal oxides are insoluble with the exception of alkali metals, CaO, SrO and BaO, all of which hydrolyze to form solutions of the corresponding metal hydroxides.
6) All hydroxides are insoluble with the exception of alkali metals and Ca2+, Sr2+ and Ba2+
7) All carbonaes (CO3 2-), phosphates (PO4 3-), sulfides (S2-) and sulfites (SO3 2-) are insoluble, with the exception of alkali metals and ammonium.
Units of concentration
percent comp. by mass: mass solute/mass solution *100 mole fraction: moles solute/total moles molarity: moles/liter molality: moles/kg normality: g/L
Arheinius definition of acids and bases
Acids as source of H+ and bases as source of OH-
Brønsted-Lowry vs Lewis
Proton donors/acceptors vs Electron donors/acceptors
pH and pOH
-log[H+] or -log[OH-]
Kw
10^-14; pH + pOH = 14
Properties of Weak acids and Bases
HA (aq) + H2O (l) –> H3O+ (aq) + A- (aq)
Ka = [H3O+][A-]/[HA]
Kb = [B+][OH-]/[BOH]
Salt formation
Acids and bases may react with each other, forming a salt and (often) water in a neutralization reaction
Hydrolysis
The reverse of a neutralization, where salt reacts with water to produce the acid and base
Amphoteric species
Can act as either an acid or a base depending on chemical environment
Titration
A procedure used to determine the molarity of an acid or base by reacting a known volume of a solution of unknown concentration with a known volume of a solution with a known concentration. The half-equivalence point defines pH = pKa
Henderson-Hasselbach Equation
Used to estimate the pH of a solution in the buffer region where the concentrations of the species and its conjugate are present in approximately equal concentrations
pH = pka + log [A-]/[HA] or pOH = pKb + log [BH+/B]
Oxidation vs reduction
loss of electrons vs gain of electrons
Oxidizing agent vs reducing agent
is reduced vs is oxidized
Galvanic cells
∆G is negative; supply energy used to do work; place oxidation-reduction half reactions in separate containers (half cells) and connect allowing the flow of electrons
Electrolytic cells
Nonspontaneous –> electrical energy is required to induce a reaction; everything in one container.
Reduction potential
The tendency of a species to acquire electrons and be reduced; standard reduction potentials calculated under standard conditions (25˚C, 1 atm, 1 M)
E˚cell or emf
emf = E˚red,cathode - E˚red, anode
Spontaneity of electrochemistry
∆G = -nFEcell
Sn1
2 steps; likes polar protic solvents; 3˚ > 2˚ > 1˚ > methyl; rate = k[RL]; racemic products; strong nucleophile not required
Sn2
1 step; likes polar aprotic solvents; methyl > 1˚ > 2˚ > 3˚; rate = k[Nu][RL]; optically active and inverted products; favored with strong nucleophile