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Question 1
1.
Consider the following equilibrium:
½N2O4(g)
NO2(g); Kc = 3.3 at 100°C
For which of the following equilibria is Kc less than 3.3 at 100°C?
Answer
2N2O4(g)
N2O4(g)
4NO2(g)
2NO2(g)
4N2O4(g)
8NO2(g)
3N2O4(g)
6NO2(g)
¼N2O4(g)
½NO2(g)
6.7 points
Question 2
1.
For the reaction
IO3–(aq) + 5I–(aq) + 6H+(aq) → 3I2(aq) + 3H2O(l)
the rate of disappearance of IO3–(aq) at a particular time and concentration is 2.4 × 10 -3 mol/(L ·
s). What is the rate of appearance of I2(aq)?
Answer
–7.2 × 10-3 mol/(L · s)
2.4 × 10-3 mol/(L · s)
7.2 × 10-3 mol/(L · s)
8.0 × 10-3 mol/(L · s)
1.3 × 10-3 mol/(L · s)
6.7 points
Question 3
1.
The strongest intermolecular forces between molecules of PH3 are
Answer
ionic bonds.
hydrogen bonds.
dipole–dipole attractions.
London forces.
covalent bonds.
6.7 points
Question 4
1.
Which of the following equilibria would be affected by volume changes at constant temperature?
Answer
C2H4(g) + H2(g)
C2H6(g)
SO3(g) + NO(g)
NO2(g) + SO2(g)
2HCl(g)
2HF(g)
H2(g) + Cl2(g)
H2(g) + F2(g)
HCl(aq) + NaOH(aq)
6.7 points
H2O(l) + NaCl(aq)
Question 5
1.
Which of the following is not a colligative property?
Answer
freezing-point lowering
boiling-point elevation
solute solubility
osmotic pressure
vapor-pressure lowering
6.7 points
Question 6
1.
For the elementary reaction A + B → C + D, what is the predicted rate law?
Answer
Rate = k[A][B]
Rate = k[A]2
Rate = k[B]2
Rate = k
Rate = k[A]/[C]
6.7 points
Question 7
1.
Consider the combustion of methane (as represented by the following equation). This is the
reaction that occurs for a Bunsen burner, which is a source of heat for chemical reactions in the
laboratory.
CH4(g) + 2O2(g)
CO2(g) + 2H2O(g)
For the system at chemical equilibrium, which of the following explains what happens if the
temperature is raised?
Answer
The equilibrium position is shifted to the right, and the value for K increases.
The equilibrium position is shifted to the right, and the value for K decreases.
The equilibrium position is shifted to the left, and the value for K decreases.
The equilibrium position is shifted to the left, and the value for K increases.
The equilibrium position is shifted, but the value for K stays constant.
6.7 points
Question 8
1.
The fact that the boiling point of a pure solvent is lower than the boiling point of a solution of the
same solvent is a direct consequence of the
Answer
vapor pressure of the solution being higher than the vapor pressure of the pure solvent.
vapor pressure of the solution being lower than the vapor pressure of the pure solvent.
osmotic pressure of the solvent being higher than the osmotic pressure of the solution.
osmotic pressure of the solvent being lower than the osmotic pressure of the solution.
freezing-point depression of the solution.
6.7 points
Question 9
1.
Given the equilibrium constants for the following reactions:
4Cu(s) + O2(g)
2Cu2O(s); K1
4CuO(s)
2Cu2O(s) + O2(g); K2
What is K for the system
2Cu(s) + O2(g)
equivalent to?
2CuO(s)
Answer
K1 × K2
{(K2)/(K1)}½
{(K1)/(K2)}½
(K2)½/(K1)
(K1)(K2)½
6.7 points
Question 10
1.
Consider the following equilibrium:
O2(g) + 2F2(g)
2OF2(g); Kp = 2.3 × 10–15
Which of the following statements is true?
Answer
If the reaction mixture initially contains only OF2(g), then the total pressure at equilibrium
will be less than the total initial pressure.
If the reaction mixture initially contains only O2(g) and F2(g), then at equilibrium, the
reaction mixture will consist of essentially only OF2(g).
If the reaction mixture initially contains only O2(g) and F2(g), then the total pressure at
equilibrium will be greater than the total initial pressure.
If the reaction mixture initially contains only OF2(g), then at equilibrium, the reaction
mixture will consist of essentially only O2(g) and F2(g).
For this equilibrium, Kc = Kp.
6.7 points
Question 11
1.
Which of the following pure substances is a solid at room temperature and pressure?
Answer
NH3
PH3
AlH3
CH4
SiH4
6.7 points
Question 12
1.
A sulfuric acid solution that is 65.0% H2SO4 by mass has a density of 1.55 g/mL at 20°C. What is
the molality of sulfuric acid in the solution?
Answer
0.0243 m
41.1 m
1.01 m
0.650 m
18.9 m
6.7 points
Question 13
1.
A 3.140 molal solution of NaCl is prepared. How many grams of NaCl are present in a sample
containing 2.901 kg of water?
Answer
910.9 g
155.9 g
322.9 g
532.3 g
none of these
6.7 points
Question 14
1.
In a first-order reaction, the half-life is 132 minutes. What is the rate constant?
Answer
8.75 × 10-5 s-1
1.26 × 10-4 s-1
5490 s-1
0.315 s-1
5.25 × 10-3 s-1
6.7 points
Question 15
1.
In the reaction 2H2O2(aq) → 2H2O(l) + O2(g), the initial concentration of H2O2 is 0.519 M and,
26.2 s later, the concentration of H2O2 is 0.365 M. What is the initial rate of the reaction?
Answer
0.00588 M/s
–0.00294 M/s
–0.00588 M/s
0.00294 M/s
0.0139 M/s
6.7 points
Question 16
1.
When cobalt chloride is added to pure water, the Co 2+ ions hydrate. The hydrated form then reacts
with the Cl– ions to set up the equilibrium shown here:
Co(H2O)62+ + 4Cl–
(pink)
CoCl42– + 6H2O
(blue)
Which statement describes the change that the system will undergo if silver nitrate is added?
Answer
It should become more blue.
It should become more pink.
Water will be produced.
The silver ion will react with the CoCl42–.
Nothing will change.
6.7 points
Question 17
1.
The following equilibrium is exothermic. How could the yield of diiodine pentoxide be increased?
I2(g) + 5CO2(g)
5CO(g) + I2O5(g)
Answer
by increasing the pressure
by decreasing the pressure
by increasing the temperature
by decreasing the temperature
by decreasing the volume of the reaction vessel
6.7 points
Question 18
1.
The following data were obtained for the hypothetical reaction 2A + B → products.
[A]0 (M)
[B]0 (M)
Initial Rate (M/s)
0.2
0.1
5
0.2
0.2
20
0.6
0.1
15
What is the overall order of this reaction?
Answer
0
1/2
1
4
3
6.7 points
Question 19
1.
The phrase "the heat absorbed or released by a system undergoing a physical or chemical change
at constant pressure" is
Answer
the definition of a state function.
the change in enthalpy of the system.
a statement of Hess's law.
the change in internal energy of the system.
the temperature change of the system.
6.7 points
Question 20
1.
A first-order chemical reaction is observed to have a rate constant of 32 min-1. What is the
corresponding half-life for the reaction?
Answer
46 min
1.3 min
45.8 s
1.3 s
1.9 s
6.7 points
Question 21
1.
For the equilibrium N2O4(g)
2NO2(g), at 298 K, Kp = 0.15. For this reaction system, it is
found that the partial pressure of N2O4 is 3.5 10-2 atm at equilibrium. What is the partial
pressure of NO2 at equilibrium? (R = 0.0821 L · atm/(K · mol))
Answer
0.0053 atm
23 atm
0.072 atm
0.0018 atm
4.8 atm
6.7 points
Question 22
1.
The metal iron crystallizes in a body-centered cubic lattice. If the density of iron is 7.87 g/cm3,
what is the atomic volume of iron?
Answer
8.02 × 106 pm3
1.44 × 105 pm3
4.01 × 106 pm3
1.59 × 105 pm3
7.96 × 104 pm3
6.7 points
Question 23
1.
For the endothermic reaction 2CO2(g) + N2(g)
2NO(g) + 2CO(g), the conditions that
favor maximum conversion of the reactants to products are
Answer
high temperature and high pressure.
high temperature, pressure being unimportant.
high temperature and low pressure.
low temperature and high pressure.
low temperature and low pressure.
6.7 points
Question 24
1.
Two substances A and B react with each other in such a way that one-half of A remains after 25
min and one-fourth of A remains after 50 min. Doubling the concentration of B while keeping the
concentration of A fixed doubles the rate of the reaction. This reaction is
Answer
zero-order in both A and B.
first-order in both A and B.
first-order in A and second-order in B.
second-order in A and first-order in B.
second-order in both A and B.
6.7 points
Question 25
1.
The formation reaction for NH3(g) is
Answer
N(g) + 3H(g) → NH3(g).
N(g) +
H2(g) → NH3(g).
N2(g) + 3H(g) → NH3(g).
N2(g) +
H2(g) → NH3(g).
N2(g) + H2(g) → NH3(g).
6.7 points
Question 26
1.
The molecules in a sample of solid SO2 are attracted to each other by a combination of
Answer
London forces and H-bonding.
H-bonding and ionic bonding.
covalent bonding and dipole-dipole interactions.
London forces and dipole-dipole interactions.
none of these
6.7 points
Question 27
1.
Below is a phase diagram for a substance.
Which line represents the melting-point curve of the substance?
Answer
M-N
R-X
X-Z
S-X
S-Z
6.7 points
Question 28
1.
What is the mass percent of ethylene glycol (HOCH2CH2OH) in a solution of ethylene glycol in
water that has a freezing point of –15.0°C? (Kf for water is 1.858°C/m.)
Answer
33.4%
99.8%
8.07%
50.1%
76.9%
6.7 points
Question 29
1.
When 0.0400 mol of HCl(aq) is reacted with 0.0400 mol of NaOH(aq) in 50.0 mL of water, the
temperature of the solution increases by 5.56°C. What is the enthalpy of reaction for the following
thermochemical equation?
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
Assume that the heat capacity of the solution and calorimeter is 401.5 J/°C.
Answer
–55.8 kJ
–2.23 kJ
2.23 kJ
55.8 kJ
–0.0893 kJ
6.7 points
Question 30
1.
Consider the following equilibrium:
4NH3(g) + 3O2(g)
2N2(g) + 6H2O(g)
Suppose 0.30 mol of NH3 and 0.40 mol of oxygen are added to a 5.0-L container. If x mol of water
is present at equilibrium, how many moles of ammonia will remain at equilibrium?
Answer
0.30 – x
0.40 –
x
x
0.30 –
x
0.30 –
x