My Old GCHEM + OCHEM flashcards
Are intermediates allowed to appear in the rate law?
No.
Name the 2 different “forms” of the gas constant. Also, name the conditions at STP.
R = 0.0821 (L atm) / (mol K)
R = 8.314 J / (mol K), (where P is in Pascals and V is in m3)
STP: 0° C , 1 atm pressure
Are S° values smaller or larger for more complex molecules?
S° values are larger for more complex molecules.
What is Henry’s law?
Solubility = kP
Solubility = molar solubility of a gas in a liquid.
k = constant (specific to each gas and temp).
P = partial pressure of the gas over the solution.
What is the equation that relates Kp to Kc?
Kp = Kc (RT)Δn
Δn = change in number of moles of gas.
What is the “normal” form of the Arrhenius equation?
k = Ae (–Ea)/(RT)
A is the frequency factor
e is the mathematical e
Ea is the activation energy
k is the rate constant
What is the integrated rate law for a first order reaction?
ln [A]t = –kt + ln [A]0
What happens halfway to the equivalence point of a titration?
pH = pKa
What is the equation for osmotic pressure?
Π = iMRT
Π is the osmotic pressure.
i is the van’t Hoff factor.
M is the molarity.
R is the gas constant.
T is the temperature.
Are catalysts allowed to appear in the rate law?
Yes.
What are the units of k for a second order reaction?
1 / (M sec)
What is ΔG°f ?
ΔG°f is the standard free energy of formation.
ΔG°f is zero for an element in its most stable form at 25°C.
What are the units of k for a zero order reaction?
M / sec
What is the purpose of the Arrhenius equation?
It lets you calculate the activation energy of a reaction, based on the rate constants at two different temperatures.
How do the following compounds compare in terms of acidity:
HClO, HClO2, HClO3, and HClO4
Why?
Low Acidity HClO < HClO2 < HClO3 < HClO4 High Acidity
The reason is due to oxidation number. HClO4 has the most highly oxidized atom bonded to the oxygen with the proton.
How does entropy change as temperature increases?
The entropy of a substance increases with increasing temperature.
What is Graham’s law of effusion for two gases?
What does the symbol D mean in chemistry? What can be calculated from it, and how?
D is the bond dissociation energy.
D is always positive, because energy must always be supplied in order to break a bond.
ΔH°rxn = D(reactant bonds) – D(product bonds)
Define critical point.
The spot on a phase diagram where the liquid/gas boundary line abruptly ends (supercritical fluid is formed above this line).
What is the second law of thermodynamics?
In any spontaneous process, the total entropy of a system and its surroundings always increases.
What is the “linear” form of the Arrhenius equation?
ln k = (-Ea/R) (1/T) + ln A
y = m x + b
A is the frequency factor
Ea is the activation energy
k is the rate constant
What is the rate law for a first order reaction?
Rate = k [A]
What is the half-life of a zero order reaction?
t1/2 = [A]0 / (2k)
What is the Clausius-Clapeyron equation?
What is it useful for?
ln Pvap = ( –ΔHvap / R ) ( 1 / T ) + C
y = m x + b
Pvap is the vapor pressure.
ΔHvap is the heat of vaporization.
C is a constant (not related to heat capacity).
This equation lets you calculate ΔHvap if Pvap is known at two different temperatures.
What is Raoult’s law?
PA = XAPA°
PA is the partial pressure exerted by component A in the solution.
PA° is the vapor pressure of pure A.
XA is the mole fraction of A in the solution.
What is the first law of thermodynamics?
The total internal energy E of an isolated system is constant.
What is the link (in equation form) between kinetics and equilibrium?
Kc = (kfor) / (krev)
What is the advantage of using molality?
It doesn’t depend on temperature, like molarity does.
What is the equation for boiling point elevation and freezing point depression?
ΔTb = Kb m i
ΔTf = Kf m i
ΔT is the change in boiling or freezing point.
Kb is the molal boiling point elevation constant.
m is the molality of the solution.
i is the van’t Hoff factor (mol in solution / mol dissolved).
Name all the units of pressure, and what they are equal to at standard atmospheric pressure.
1 atm = 760 mm Hg
760 mm Hg = 760 torr
1 atm = 101,325 Pa (N / m2)
1 bar = 100,000 Pa
What happens when AgCl is added to pure water? What happens when NH3 is added?
AgCl is insoluble in pure water, but dissolves when NH3 is added. This happens because the Ag+ forms a complex ion (via coordinate covalent bonds) with the NH3.
Define IP.
IP = Ion Product. It is basically Q for a solubility equilibrium.
Define ΔS°.
ΔS° is the standard entropy of reaction.
ΔS° = S°products – S°reactants
What is the relationship between ΔG, ΔG°, K, and Q?
ΔG = ΔG° + RT lnQ
At equilibrium, ΔG = 0 and K = Q, so:
ΔG° = –RT lnK
What is the rate law for a second order reaction?
Rate = k [A]2
What does the rate law for a generic reaction look like?
Rate = k [A]m [B]n
What is Graham’s law of effusion for one gas?
The rate of effusion of a gas is inversely proportional to the square root of the molar mass of the gas.
What is the integrated rate law for a zero order reaction?
[A]t = –kt + [A]0
What happens at the equivalence point of a titration?
Equal moles of acid and base have been added.
What does the symbol µ mean in chemistry? How is it calculated?
µ = the dipole moment
µ = (Q) x (r)
µ is given in units of Debyes (C m)
Q = charge at either end of dipole, in Coulombs
r = distance between charges
How do the following compounds compare in terms of acidity:
HF, HCl, HBr, and HI
Why?
Low Acidity HF << HCl < HBr < HI High Acidity
The reason is due to bond strength. HI has the weakest bond.
What is the third law of thermodynamics?
The entropy of a perfectly ordered crystalline substance at 0 K is zero.
What are the units of k for a first order reaction?
1 / sec
Name 6 strong acids.
HCl, HBr, HI, HClO4, HNO3, and H2SO4.
Define effusion.
When a gas escapes from a container through a pinhole into a vacuum, without molecular collisions.
Are products allowed to appear in the rate law?
Yes.
How do the following compounds compare in terms of acidity:
HOCl, HOBr, and HOI
Why?
Low Acidity HOI < HOBr < HOCl High Acidity
The reason is due to electronegativity. HOCl has the most electronegative atom bonded to oxygen.
What is the half-life of a first order reaction?
t1/2 = (ln2 / k)
ln2 = 0.693
What is the integrated rate law for a second order reaction?
[A]t-1 = kt + [A]0-1
How do you calculate the overall reaction order for a reaction?
You take the sum of all the exponents in the rate law.
Describe the solid/liquid boundary line on a phase diagram. When is it positive, and when is it negative?
The slope is positive for most substances (example = CO2).
The slope is negative for water, because ice is less dense than water. Therefore, when pressure is increased at constant temp, ice turns back into water.
Define S°.
S° is the standard molar entropy. It is defined as the entropy of 1 mol of a pure substance at 1atm and a specified temperature, usually 25° C.
What is the mathematical definition of ΔH?
ΔH = qp
The subscript p signifies constant pressure.
Are reactants allowed to appear in the rate law?
Yes.
What is the rate law for a zero order reaction?
Rate = k
How do successive half-lives change for a zero order reaction, a first order reaction, and a second order reaction?
Zero order: Each successive half-life is half as long as the last.
First order: Each successive half-life is the same as the last.
Second order: Each successive half-life is twice as long as the last.
What is the half-life of a second order reaction?
t1/2 = (k [A]0)-1
Explain what it means if Q is greater than, less than, and equal to K.
If Kc > Qc, more products will form.
If Kc < Qc, more reactants will form.
(Write K and Q in alphabetical order, then the < or > acts as the head of the arrow, indicating which way the reaction will proceed)
If Kc = Qc, the system is at equilibrium.
How do you calculate ΔG° ?
ΔG° = ΔG°f (products) – ΔG°f (reactants)
What does it mean for a substance if its ΔG°f < 0 ?
It means that the substance is stable and will not decompose to its constituent elements under standard-state conditions.
Explain how to use VSEPR to determine molecular geometry.
Double and triple bonds count the same as single bonds.
Lone pairs spread out and occupy more space than bonding pairs, so put them as far apart as possible.
3 charge clouds: Bond angles = ~120°
4 charge clouds: Bond angles = ~109.5°
5 charge clouds: Bond angles = 90° and 120°
What are the possible geometries for a molecule with 2 charge clouds?
Linear.
What are the possible geometries for a molecule with 3 charge clouds?
Bent, or trigonal planar.
What are the possible geometries for a molecule with 4 charge clouds?
Tetrahedral, trigonal pyramidal, or bent.
What are the possible geometries for a molecule with 5 charge clouds?
Trigonal bipyramidal, seesaw, T-shaped, or linear.
What are the possible geometries for a molecule with 6 charge clouds?
Octahedral, square pyramidal, or square planar.
What is the geometry of SF4?
Seesaw (the lone pair spreads out and occupies more space than the bonding pairs, so the lone pair wants to be as far from other things as possible).
What is the geometry of ClF3?
T-shaped.
What is the geometry of I3– ?
Linear.
What is the geometry of XeF4?
Square planar (the lone pairs spread out and occupy more space than the bonding pairs, so the lone pairs want to be as far away from each other as possible).
Give 2 definitions of the word “amphoteric”. One is more general, and one is rather specific.
- When a substance can exhibit both acidic and basic properties.
- Certain metal hydroxides are soluble in strong acid or strong base, but not in a neutral solution.
Define bond length.
The optimum distance between nuclei, where net attractive forces are maximized.
Define lattice energy. How do ionic radii and magnitude of ionic charges affect lattice energy?
It is the enthalpy change that occurs when 1 mol of ionic solid is separated into gaseous ions.
Smaller ionic radii lead to higher lattice energies.
Larger ionic charges lead to higher lattice energies.
Explain the difference between intensive and extensive properties.
Intensive properties do not depend on the size of the sample (examples = density, melting point).
Extensive properties depend on the size of the sample (examples = mass, volume).
What is the formula for hydrogen phosphate?
HPO42-
What is the formula for perchlorate?
ClO4–
What is the formula for chlorite?
ClO2–
What is the formula for peroxide?
O22–
What is the formula for sulfite?
SO32–
What is the formula for thiosulfate?
S2O32–
What is the formula for phosphate?
PO43–
What is the formula for chlorate?
ClO3–
What is the formula for dihydrdogen phosphate?
H2PO4–
What is the formula for nitrite?
NO2–
What is the formula for permanganate?
MnO4–
What is the formula for hydrogen sulfate?
HSO4–
What is the formula for nitrate?
NO3–
