Multiple Choice
Identify the
letter of the choice that best completes the statement or answers the question.
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1.
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Which
statement concerning relative rates of reaction is correct for the decomposition of
phosphine?
4 PH3(g) →
P4(g) + 6 H2(g)
a. | The rate of disappearance of PH3 is 6/4 the rate of
appearance of H2. | b. | The rate of appearance of P4 is equal to the rate of
appearance of H2. | c. | The rate of disappearance of PH3 is
¼ the rate of
appearance of P4. | d. | The rate of disappearance of PH3 is 4 times the rate
of appearance of H2. | e. | The rate of appearance of H2 is 6 times the rate of
appearance of P4. | | |
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2.
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Which
of the following expressions relates the rates of reaction of NOCl(g) and
Cl2(g)?
2 NOCl(g)
→ 2 NO(g) + Cl2(g)
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3.
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For
the reaction A + 2B
→ C, the rate law is
 =
k[A][B]2.
What are the
units of the rate constant where time is measured in seconds?
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4.
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The
reaction of NO and O2 produces NO2.
2 NO(g) + O2(g)
→ 2 NO2(g)
The reaction is second-order with respect to NO(g) and first-order
with respect to O2(g). At a given temperature, the rate constant, k, equals 6.1 x
103 M-2s-1. What is the rate of reaction when the initial
concentrations of NO and O2 are 0.020 M and 0.015 M, respectively? a. | 9.8 x
10-10 M/s | b. | 0.027 M/s | c. | 0.037
M/s | d. | 1.0
M/s | e. | 1.8
M/s | | |
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5.
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The
half-life of a first-order decomposition reaction is 2.36 hours. If the initial concentration of
reactant is 0.52 M, what is the concentration of reactant after 752 seconds? a. | 0.046
M | b. | 0.16
M | c. | 0.26
M | d. | 0.47
M | e. | 0.49
M | | |
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6.
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What
is the rate constant for a first-order reaction if the half-life of the reaction is 6.43 x
10-5 seconds? a. | 9.28 x 10-5 s-1 | b. | 0.0967
s-1 | c. | 10.3 s-1 | d. | 1.08 x
104 s-1 | e. | 1.56 x 104 s-1 | | |
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7.
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For
the first-order decomposition of N2O5 at 340 K, where k = 5.8 x
10-3 s-1, calculate the original concentration if the concentration of
N2O5 is 0.41 M after 209 seconds. a. | 0.12
M | b. | 0.23
M | c. | 0.72
M | d. | 1.4
M | e. | 1.7
M | | |
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8.
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Hydrogen peroxide decomposes into water and oxygen in a first-order
process.
H2O2(aq)
→
H2O(l) + ½ O2(g)
At 20.0 °C, the half-life for the reaction is 3.92 x
104 seconds. If the initial concentration of hydrogen peroxide is 0.88 M, what is the
concentration after 2.20 days? a. | 0.00 M | b. | 0.031
M | c. | 018
M | d. | 0.44
M | e. | 0.88
M | | |
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9.
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The
decomposition of formic acid follows first-order kinetics.
HCO2H(g)
→ CO2(g) +
H2(g)
The half-life for the reaction at 550 °C is 24 seconds.
How many seconds does it take for the formic acid concentration to decrease by 75%? a. | 6.0
s | b. | 18
s | c. | 24
s | d. | 36
s | e. | 48
s | | |
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10.
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What
is the half-life of a first-order reaction with a rate constant of 0.457
s-1? a. | 0.659
s | b. | 0.783
s | c. | 1.48
s | d. | 1.52
s | e. | 2.19
s | | |
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11.
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For a
chemical reaction, the activation energy for the forward reaction is +112 kJ and the activation
energy for the backward reaction is +187 kJ. What is the overall energy change for the forward
reaction? a. | -299
kJ | b. | -75
kJ | c. | -0.599
kJ | d. | +75
kJ | e. | +299
kJ | | |
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12.
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Given
the initial rate data for the reaction A + B → C, determine the rate expression for the
reaction.
[A], M | [B],
M | | 0.250 | 0.150 | 8.90 x
10-6 | 0.250 | 0.300 | 1.78 x
10-5 | 0.500 | 0.300 | 7.12 x
10-5 | | | |
a. |  = 2.37 x
10-4 M-1s-1 [A][B] | b. |  = 9.49 x 10-4 M-2s-1
[A]2[B] | c. |  = 1.58 x
10-3 M-2s-1 [A][B]2 | d. |  = 6.33 x 10-3 M-3s-1
[A]2[B]2 | e. |  = 3.80 x
10-3 M-3s-1 [A]3[B] | | |
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13.
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For
the reaction A
→ B, the rate law is
 =
k[A].
What are the units of the rate constant where time is
measured in seconds?
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14.
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A
student analyzed a first-order reaction and obtained the graph below. Unfortunately, the student
forgot to label the axes. What are the correct labels for the x and y
axes?
a. | x axis = time, y
axis = ln[A] | b. | x axis = time, y axis = [A] | c. | x axis = time, y
axis = 1/[A] | d. | x axis = 1/Time, y axis = [A] | e. | x axis = 1/Time,
y axis = 1/[A] | | |
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15.
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In
basic solution, (CH3)3CCl reacts according to the equation
below.
(CH3)3CCl + OH-
→
(CH3)3COH + Cl-
The accepted mechanism for the reaction
is
(CH3)3CCl
→(CH3)3C+ + Cl- (slow)
(CH3)3C+ + OH-
→
(CH3)3COH (fast)
What is a rate law that is consistent with the mechanism for this
reaction? a. | rate =
k[(CH3)3CCl] | b. | rate =
k[(CH3)3CCl][OH-] | c. | rate =
k[(CH3)3C+][OH-] | d. | rate =
k[(CH3)3CCl][OH-]/[Cl-] | e. | rate =
k[(CH3)3CCl] [OH-]/[Cl-] | | |
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16.
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If the
reaction rate for S2Cl2 + CCl4 → CS2 +
3Cl2 is first order in S2Cl2 and second order in CCl4,
then a. | rate =
k[S2Cl2][CCl4]2 | b. | the rate doubles when
the [S2Cl2] is doubled. | c. | the rate increases by a
factor of four when [CCl4] is doubled. | d. | Each of the above
statements is true. | e. | None of the above statements is true. | | |
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17.
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The
half-life for the radioactive decay of carbon-14 is 5730 years, while that of hydrogen-3 is 12.3
years. This means that a. | hydrogen decays at a faster rate than does
carbon. | b. | carbon decay is a higher order reaction than hydrogen
decay. | c. | more carbon than hydrogen is present in the
world. | d. | the concentration of hydrogen is greater than the concentration of
carbon. | e. | None of the above | | |
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18.
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Given
the initial rate data for the decomposition reaction,
A → B + C
determine the rate expression for the
reaction.
[A], M |
-Δ[A]/Δt M/s | 0.110 | 7.81
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10-3 | 0.220 | 3.12
´
10-2 | 0.330 | 7.03
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10-2 | | |
a. |  = 7.10 ´ 10-2s-1[A] | b. |  = 0.645 M-1s-1[A]2 | c. |  = 3.63 ´
10-2M-1s-1[A]2 | d. |  = 3.63 ´ 10-2M s-1 | e. |  = 5.87 M-2s-1[A]3 | | |
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19.
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Given
the initial rate data for the reaction A + B → C, determine the rate expression for the
reaction.
[A], M | [B],
M | | 0.334 | 0.134 | 4.11
´
10-9 | 0.334 | 0.187 | 8.00
´
10-9 | 0.668 | 0.134 | 4.11
´
10-9 | | | |
a. |  = 2.75 ´ 10-7
M-2s-1[A]2[B] | b. |  = 3.07 ´ 10-8 s-1[B] | c. |  = 2.29 ´ 10-7
M-1s-1[B]2 | d. |  = 6.85 ´ 10-7
M-2s-1[A][B]2 | e. |  = 1.23 ´ 10-8 s-1[A] | | |
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20.
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For
the reaction 2A + B → C, the rate law is
 =
k[A]2[B].
Which of the
factor(s) will affect the value of the rate constant for this
reaction?
1. | Increasing the concentration of reactant
A | 2. | Adding a
catalyst | 3. | Increasing the
temperature | | |
a. | 1
only | b. | 2
only | c. | 3
only | d. | 2 and
3 | e. | 1, 2, and
3 | | |
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21.
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For a
second-order decomposition reaction,
2A
→ B rate =
k[A]2
which of the
following functions can be plotted versus time to give a straight line? a. | [A] | b. | [A]2 | c. | ln | d. | ln[A] | e. | | | |
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22.
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The
reaction A → B follows first-order kinetics with a half-life of 21.7 seconds. If
the concentration of A is 0.430 M after 14.5 seconds, what is the initial concentration of
A? a. | 0271
M | b. | 0.287
M | c. | 0.644
M | d. | 0.683
M | e. | 1.59
M | | |
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23.
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For
the zero-order reaction below, a graph of ____ versus time will generate a straight
line.
A →
B + C rate = k[A]0
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24.
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The
elementary steps for the catalyzed decomposition of dinitrogen monoxide are shown
below.
N2O(g) + NO(g)
→
N2(g) + NO2(g)
2 NO2(g) → 2 NO(g) +
O2(g)
Which of the following statements are
CORRECT?
1. | The overall balanced reaction is 2 N2O(g)
→ 2
N2(g) + O2(g). | 2. | NO(g) is a catalyst for the reaction. | 3. | N2(g) is a reaction
intermediate. | | |
a. | 1
only | b. | 2
only | c. | 3
only | d. | 1 and
2 | e. | 1, 2, and
3 | | |
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25.
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In
basic solution, (CH3)3CCl reacts according to the equation
below.
(CH3)3CCl + OH-
→
(CH3)3COH + Cl-
The accepted mechanism for the reaction
is
(CH3)3CCl →
(CH3)3C+ + Cl- (slow)
(CH3)3C+ + OH-
→
(CH3)3COH (fast)
What is a rate law that is consistent with the mechanism for this
reaction? a. | rate =
k[(CH3)3CCl] | b. | rate =
k[(CH3)3CCl][OH-] | c. | rate =
k[(CH3)3C+][OH-] | d. | rate =
k[(CH3)3CCl][OH-]/[Cl-] | e. | rate =
k[(CH3)3CCl] [OH-]/[Cl-] | | |
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