1
1. (6 pts) Select the rate law that corresponds to the data shown for the following
reaction:
A + B → C
Experiment / [A]/M / [B]/M / Initial rate(M/s)1 / 0.012 / 0.035 / 0.10
2 / 0.024 / 0.070 / 0.80
3 / 0.024 / 0.035 / 0.10
4 / 0.012 / 0.070 / 0.80
a) Rate = k[B]4
b) Rate = k[A][B]3
c) Rate = k[A]2[B]2
d) Rate = k[B]3
e) Rate = k[B]
2. (6 pts) What is the value of the rate constant in question 1?
a) 4.5 b) 340 c) 3.2 x103 d) 2.3 x 103 e) 2500
3. (6 pts) What are the units for the rate constant calculated in question 2?
a) M2s b) M2s-1 c) M-1s-2 d) M-2s-1 e) M-1s-1
4.(4 pts) For a first-order reaction, a plot of ____ versus ____ is linear.
a) ln [A]t, 1/t
b) ln [A]t, t
c) 1/[A], t
d) [A], t
e) t, 1/[A]
5. (6 pts) The rate constant for the decomposition of N2O5 is 6.2 x 10-4 min-1. After 3354 min what percent of N2O5 remains? The reaction, given below, is first-order in N2O5.
N2O5→ NO2 + NO3
a) 6.25% b) 10.0% c) 12.5% d) 20.0% e) 25.0%
6. (6 pts) The rate constant for a particular second-order reaction is 0.476 L/mol-s. If the initial concentration of reactant is s 0.25 mol/L, it takes ______s for the concentration to decrease to 0.13 mol/L.
a) 7.8 b) 1.4 c) 3.7 d) 1.7 e) 0.13
7.(7 pts) A reaction with activation energy of 123 kJ/mol has a rate constant of 0.200 s-1
at 311 K. At a temperature of ____K, the rate constant will be double that at 311 K.
(R = 8.314 J/mol-K)
a) 304 b) 316 c) 622 d) 349 e) 246
8.(6 pts) Ozone is believed to decompose according to the following mechanism. What
would be the rate expression if the mechanism is correct?
2O3 (g) → 3O2(g) (balanced equation)
O3 ↔ O2 + O (fast) Step 1
O3 + O → 2O2 (slow) Step 2
a) rate = k[O3]2
b) rate = k[O3]2[O]
c) rate = k[O2]3
d) rate = k[O3]2/[O2]
e) rate = k[O3][O]
9. (6 pts) Given the following potential energy diagram for the one-step reaction:
X + Y → Z + R.
The arrow “c” represents the ______.
a) the net energy of reaction for the forward reaction
b) activation energy for the forward reaction
c) net energy of reaction for the reverse reaction
d) activation energy for the reverse reaction
e) energy content for the reaction
10. (7 pts) Consider the following hypothetical reaction and the established rate law. Select an acceptable mechanism for the reaction.
A2 + B2→ X + Y Rate = k[A2]½[B2]½
a) A2 ↔ 2A (fast) b) A2 ↔ C + X (fast) c) A2 + B2 ↔ C (fast)
B2 + A → C (slow) B2 + C → Y (slow) C → X + Y (slow)
C + A → X + Y (fast)
d) B2 → 2B (slow) e) A2 + B2 ↔ 2B (fast)
B + A2 → C (fast) B → C + X (slow)
C + B → X + Y (fast) B + C → Y (fast)
11.(7 pts) The rate constant for a particular reaction is 1.3 x 10-4 M-1s-1 at 100oC and
1.1 x 10-3 M-1s-1 at 150oC. What is the activation energy for this reaction in J/mol?
(R = 8.314 J/mol.K)
a) 1.1 x 103 b) 987 c) 5.66 x 103 d) 540 e) 5.56 x 104
12. (6 pts) The value of Kc for the equilibrium
H2(g) + I2(g) ↔ 2HI (g)
is 54.0 at 427oC. At this temperature, what is the value Kc for:
HI(g) ↔ ½ H2(g) + ½ I2(g)
a) 27 b) 7.35 c) 0.136 d) 2.92 x 103 e) 3.42 x 10-4
13. (6 pts) Consider the reaction:
4CuO(s) + CH4(g) ↔ CO2(g) + 4Cu(s) + 2H2O(g)
The value of Kc for this reaction is 1.10 at 25oC. What is the value of Kp for this
reaction? (R = 0.0821 L-atm/K-mol)
a) 658 b) 37.2 c) 26.9 d) 4.63 e) 1.52 x 10-3
14. (7 pts) 0.100 mol of N2O4 gas is placed in a 2.00-L vessel and allowed to equilibrate at 110°C. At equilibrium the concentration of NO2 is 0.072 M. Calculate the value of Kc for the reaction at this temperature.
N2O4(g) ↔ 2NO2(g)
a) 0.37 b) 1.5 c) 2.3 d) 0.57 e) 0.72
15.(8 pts) Gaseous AB3 decomposes at 1000 K to give AB and B2.
AB3(g) ↔ AB(g) + B2(g)
If 0.100 mol of AB3 is placed in a 2.00-L vessel and allowed to equilibrate at 1000 K, what will the equilibrium concentration of reactant AB3 be? (Kc = 4.08 10–3)
a) 0.0124M b) 0.0456M c) 0.0500M d) 0.0625M e) 0.0376M
16. (7 pts) The equilibrium partial pressure of PCl3 in a 3.00 L vessel that was charged
with 0.123 atm of PCl5 is ______atm if Kp = 0.0121.
PCl5(g) ↔ PCl3(g) + Cl2(g)
a) 0.078 b) 0.0450 c) 0.0900 d) 0.0330 e) 0.0657
17. (7 pts) A 1.000-L flask is filled with 1.000 mol of H2 and 2.000 mol of I2 at 448oC. The value of the equilibrium constant, Keq, for the reaction
H2(g) + I2(g) ↔ 2HI(g)
at 448oC is 50.5. What is the partial pressure of HI in atm in the flask?
(R = 0.0821 L-atm/mol-K)
a) 110.6 b) 3.85 c) 63.1 d) 234 e) 145.6
18.(6 pts) At 1000K, the value of Keq for the reaction:
2SO3(g) ↔ 2SO2(g) + O2(g)
is 0.338. Calculate the value of Q and predict the direction in which the reaction will
proceed toward equilibrium if the initial partial pressures of reactants are PSO3 = 0.16
atm; PSO2 = 0.41 atm; PO2 = 2.5 atm
a) Q > K; reaction will proceed from left to right
b) Q > K; reaction will proceed from right to left
c) Q = K; reaction will not proceed
d) Q < K; reaction will proceed from right to left
e) Q < K; reaction will proceed from left to right
19.(6 pts) Consider the following reaction at equilibrium:
2NH3(g) ↔ N2(g) + 3H2(g) ∆Ho = 92.4 kJ
This reaction will shift to the right with ______.
a) increasing both temperature and pressure
b) increasing temperature and decreasing pressure
c) decreasing both temperature and pressure
d) decreasing temperature and increasing pressure
e) the addition of extra N2 to the container
Consider the following reaction at equilibrium and then do questions 20-22:
2CO2 (g) ↔ 2CO(g) + O2(g) ∆Ho = -514 kJ
20.(6 pts) Adding O2(g) to the container will ______.
a) increase the concentration of CO(g) at equilibrium
b) decrease the concentration of CO2(g) at equilibrium
c) increase the value of the equilibrium constant
d) cause the reaction to shift to the left
e) decrease the value of the equilibrium constant
21. (6 pts) Increasing the temperature will ______.
a) increase the concentration of O2(g)
b) decrease the concentration of CO2(g)
c) decrease the value of the equilibrium constant
d) shift the reaction to the right
e) increase the concentration of CO
22.(6 pts) The yield of CO(g) in the reaction can be maximized by carrying out the
reaction ______.
a) at high temperature and high pressure
b) at high temperature and low pressure
c) at low temperature and low pressure
d) at low temperature and high pressure
e) in the presence of solid carbon
23. (6 pts) If the temperature of the following reaction is lowered from 100oC to 50oC, in
which direction will the reaction shift and how will this affect the equilibrium
constant?
H2O(g) + CO(g) ↔ H2(g) + CO2(g) + heat
a) shift in forward direction, K will increase
b) shift in reverse direction, K will increase
c) shift in forward direction, K will decrease
d) shift in reverse direction, K will decrease
e) shift in reverse direction, K will not change
24. (6 pts) A Brønstedt-Lowry base is defined as a substance that ______.
a) increases [H+] when placed in H2O
b) decreases [H+] when placed in H2O
c) increases [OH-] when placed in H2O
d) acts as a proton acceptor in any system
e) acts as a proton donor in any system.
25. (6 pts) Which one of the following would be considered a base according to the
Brønstedt-Lowry definition but not by the Arrhenius definition?
a) NH3(g) b) HBr(aq) c) Ba(OH)2(aq) d) HF(g) e) KOH(aq)
26 (6 pts) The [H+] and pH of 0.0037 M HBr at 25oC are respectively.
a) 0.0074 M, 2.43
b) 0.0037 M, 2.43
c) 0.0074 M, 2.13
d) 0.0037 M , 2.13
e) 0.0037 M, -2.13
27,(6 pts) The pH of Milk of Magnesia, Mg(OH)2, is 10.50. What is the [OH-]?
Kw = [H3O+][OH-] = 1.00 x 10-14
a) 3.2 x 10-3 b) 3.2 x 10-4 c) 5.0 x 10-5 d) 3.2 x 10-11 e) 5.0 x 10-11
28. (6 pts) What is the conjugate base of H2PO4- ?
a) H3PO4 b) H2PO4 c) H2PO4+ d) HPO4-2 e) HPO4-
29.(6 pts) Calculate the pOH of a solution that contains 1.94 x 10-10 M hydronium ions.
Kw = [H3O+][OH-] = 1.00 x 10-14
a) 1.94 b) 4.29 c) 7.00 d) 14.0 e) 9.71