Chemistry, 6e (McMurry/Fay)
Chapter 12 Chemical Kinetics
12.1 Multiple-Choice Questions
1) Which term describes the measure of the increase in the concentration of a product per unit time?
A) activation energy
B) kinetics
C) reaction rate
D) reaction time
2) “Instantaneous rate” is defined as the
A) change in concentration per unit time.
B) equation showing how the rate depends on the concentration of each reactant.
C) rate of reaction at a particular time.
D) rate of reaction during a time interval.
3) Molecular hydrogen can be made from methane gas by the reaction below. How is the rate of
disappearance of CH4 related to the rate of appearance of H2?
[CH ]
4
t
−
= ?
CH4 (g) + H2O (l) → CO (g) + 3H2 (g)
A)
[H ]
2
t
+
B)
1 [H ]
2
3 t
+
C)
[H ]
2
3t
+
D) none of these
4) Methanol can be produced by the following reaction:
CO(g) + 2 H2(g) → CH3OH(g).
How is the rate of disappearance of hydrogen gas related to the rate of appearance of methanol?
[H ]
2
t
−
= ?
A)
[H ]
4
t
+
B)
1 Δ[CH OH]
3
+2 Δt
C)
Δ[CH OH]
3
+2 Δt
D) none of these
5) Hydroquinone, HOC6H6OH, can be formed by the reaction with acetylene below:
2 HCCH + 3 CO + H2O → HOC6H4OH + CO2
How is the rate of disappearance of acetylene, HCCH, related to the appearance of hydroquinone (Hq)?
[HCCH]
t
−
= ?
A)
1 [Hq]
2 t
+
B)
2 [Hq]
3 t
+
C)
[Hq]
t
+
D)
2 [Hq]
t
+
6) For the reaction shown below, what is the relationship between the rate of formation of Br2 and the
rate of reaction of Br– over the same time period?
ClO2–(aq) + 4 Br–(aq) + 4 H+(aq)→ Cl–(aq) + 2 Br2(aq) +2 H2O(l)
A) rate of formation of Br2 = 1/2 × rate of reaction of Br–
B) rate of formation of Br2 = 1/4 × rate of reaction of Br–
C) rate of formation of Br2 = 2 × rate of reaction of Br–
D) rate of formation of Br2 = 2 × rate of reaction of Br–
7) The reaction that occurs in a Breathalyzer, a device used to determine the alcohol level in a person’s
bloodstream, is given below. If the rate of appearance of Cr2(SO4)3 is 1.24 mol/min at a particular
moment, what is the rate of disappearance of C2H6O at that moment?
A) 0.413 mol/min
B) 0.826 mol/min
C) 1.86 mol/min
D) 3.72 mol/min
8) The decomposition of dinitrogen pentoxide is described by the chemical equation
2 N2O5(g) → 4 NO2(g) + O2(g)
If the rate of disappearance of N2O5 is equal to 1.40 mol/min at a particular moment, what is the rate of
appearance of NO2 at that moment?
A) 0.700 mol/min
B) 1.40 mol/min
C) 2.80 mol/min
D) 5.60 mol/min
9) The decomposition of dinitrogen pentoxide is described by the chemical equation
2 N2O5(g) → 4 NO2(g) + O2(g)
If the rate of appearance of NO2 is equal to 0.560 mol/min at a particular moment, what is the rate of
appearance of O2 at that moment?
A) 0.140 mol/min
B) 0.280 mol/min
C) 1.12 mol/min
D) 2.24 mol/min
10) The decomposition of dinitrogen pentoxide is described by the chemical equation
2 N2O5(g) → 4 NO2(g) + O2(g)
If the rate of appearance of O2 is equal to 2.40 mol/min at a particular moment, what is the rate of
disappearance of N2O5 at that moment?
A) 0.600 mol/min
B) 1.20 mol/min
C) 4.80 mol/min
D) 9.60 mol/min
11) Hydrogen peroxide decomposes to water and oxygen according to the reaction below:
2 H2O2(aq) → 2 H2O(l) + O2(g)
In the presence of large excesses of I– ion, the following set of data is obtained. What is the average rate
of disappearance of H2O2(aq) in M/s in the first 45.0 seconds of the reaction if 1.00 L of H2O2 reacts at
25°C and 1.00 atm pressure?
A) 9.09 × 10-7 M/s
B) 3.63 × 10-6 M/s
C) 4.33 × 10-5 M/s
D) 1.64 × 10-4 M/s
12) A concentration-time study of the gas phase reaction 2 A3 → 3 A2 produced the data in the table
below.
Time (s) [A3] (M) [A2] (M)
0 4.00 × 10–4 0
10 2.00 × 10–4 3.00 × 10–4
20 1.00 × 10–4 4.50 × 10–4
30 5.00 × 10–5 ?
What is the average rate of decomposition of A3 in the time interval 20-30 seconds?
A) 4.00 × 10–4 M/s
B) 3.50 × 10–5 M/s
C) 5.00 × 10–6 M/s
D) 4.00 × 10–6 M/s
13) A concentration-time study of the gas phase reaction 2 A3 → 3 A2 produced the data in the table
below.
Time (s) [A3] (M) [A2] (M)
0 4.00 × 10–4 0
10 2.00 × 10–4 3.00 × 10–4
20 1.00 × 10–4 4.50 × 10–4
30 5.00 × 10–5 ?
What is the average rate of formation of A2 in the time interval 20-30 seconds?
A) 6.00 × 10–4 M/s
B) 5.25 × 10–5 M/s
C) 7.50 × 10–6 M/s
D) 6.00 × 10–6 M/s
14) A concentration-time study of the gas phase reaction 2 A3 → 3 A2 produced the data in the table
below.
Time (s) [A3] (M) [A2] (M)
0 4.00 × 10–4 0
10 2.00 × 10–4 3.00 × 10–4
20 1.00 × 10–4 4.50 × 10–4
30 5.00 × 10–5 ?
What is the concentration of A2 after 30 seconds?
A) 5.00 × 10–4 M
B) 5.25 × 10–4 M
C) 5.50 × 10–4 M
D) 6.00 × 10–4 M
15) Which statement is true for the general rate law: Rate = k[A]m[B]n?
A) It can be written from the stoichiometry of the overall reaction.
B) The overall order of the reaction is equal to m times n.
C) The values for the exponents must be determined by experiment.
D) The exponents in the rate law must be positive integers.
16) For the reaction shown below, what is the order of reaction with respect to Br–?
ClO2–(aq) + 4 Br–(aq) + 4 H+(aq)→ Cl–(aq) + 2 Br2(aq) +2 H2O(l)
A) 1st order
B) 2nd order
C) 4th order
D) can’t tell from the information provided
17) The reaction below is first order in H2 and second order in NO. What is the rate law for this
reaction?
2 H2(g) + 2 NO(g) → N2(g) + 2 H2O(g)
A) Rate = 2k[H2][NO]
B) Rate = k[H2][NO]2
C) Rate = k[H2]2[NO]2
D) Rate = 2k[H2]2[NO]2
18) The reaction shown below has the rate law: Rate = k[BrO3–][Br–][H+]2.
BrO3–(aq) + 5 Br–(aq) + 6 H+(aq) → 3 Br2(aq) + 3 H2O(l)
What is the overall order of reaction?
A) first
B) second
C) third
D) fourth
19) For a reaction that follows the general rate law, Rate = k[A][B]2, what will happen to the rate of
reaction if the concentration of A is increased by a factor of 3.00? The rate will
A) decrease by a factor of 1/9.00.
B) decrease by a factor of 1/3.00.
C) increase by a factor of 3.00.
D) increase by a factor of 9.00.
20) For a reaction that follows the general rate law, Rate = k[A][B]2, what will happen to the rate of
reaction if the concentration of B is increased by a factor of 2.00? The rate will
A) decrease by a factor of 1/4.00.
B) decrease by a factor of 1/2.00.
C) increase by a factor of 2.00.
D) increase by a factor of 4.00.
7
21) The reaction between chlorine and nitric oxide to form nitrosyl chloride is shown below. If the
reaction rate doubles when the concentration of Cl2 is doubled and the rate quadruples when the
concentration of NO is doubled, by what factor will the rate increase if both concentrations, NO and Cl2,
are doubled?
Cl2(g) + 2 NO(g) → 2 NOCl(g)
A) 2
B) 4
C) 8
D) 16
22) The hydrolysis of tert-butyl chloride is given in the reaction below:
(CH3)3CCl(aq) + H2O(l) → (CH3)3COH(aq) + H+(aq) + Cl–(aq)
If the rate law is: Rate = k[(CH3)3CCl], what is the order of the reaction with respect to water?
A) zero
B) first
C) second
D) third
23) Given the following hypothetical reaction: 2 E(g) + F(g) + G(g) → products.
If the rate law is: Rate = k[E]2[F]-1, what is the order of reaction with respect to E?
A) zero
B) first
C) second
D) third
24) Given the following hypothetical reaction: 2 E(g) + F(g) + G(g) → products.
If the rate law is: Rate = k[E]2[F]-1, what is the overall order of reaction?
A) zero
B) first
C) second
25) The decomposition of ammonia to nitrogen and hydrogen on a tungsten filament at 800°C is
independent of the concentration of ammonia at high pressures of ammonia. What is the order of the
reaction with respect to ammonia?
A) zero
B) first
C) second
D) third
26) Cerium(IV) ion reacts with thallium(I) ion in a one-step reaction shown below:
2 Ce4+(aq) + Tl+(aq) → 2 Ce3+(aq) + Tl3+(aq).
If the rate law is: Rate = k[Ce4+]2[Tl+], what is the overall order of the reaction?
A) first
B) second
C) third
D) fourth
27) What is the overall reaction order for the reaction that has the rate law: Rate = k[H2][NO]2?
A) zero order
B) first order
C) second order
D) third order
28) Iodide and hypochlorite ion react in aqueous solution according to the reaction below:
I– + OCl– → OI– + Cl–
If the concentration of OH– in the solution is doubled, the rate of the reaction is halved. What is the
order of the reaction with respect to OH–?
A) -2
B) -1
C) +1
D) +2
29) Chlorine reacts with chloroform according to the reaction given below:
Cl2 + CHCl3 → CCl4 + HCl
When the initial concentration of Cl2 is doubled the reaction rate increases by a factor of 1.41. What is
the order of the reaction with respect to Cl2?
A) -1/2
B) -1
C) 1/2
D) 2
30) If the units for rate are M s-1, what are the units for the rate constant, k, if the overall order of the
reaction is three?
A) s-1
B) M2 s-1
C) M-1 s-1
D) M-2 s-1
31) Using the method of initial rates for the reaction A → B, if the initial concentration of A is doubled
and the rate of reaction quadruples, what is the order of reaction with respect to A?
A) zeroth
B) first
C) second
D) fourth
32) The following set of data was obtained by the method of initial rates for the reaction:
2 HgCl2(aq) + C2O42-(aq) → 2 Cl–(aq) + 2 CO2(g) + Hg2Cl2(s)
What is the rate law for the reaction?
A) Rate = k[HgCl2][C2O42-]-2
B) Rate = k[HgCl2][C2O42-]-1
C) Rate = k[HgCl2]2[C2O42-]
D) Rate = k[HgCl2][C2O42-]2
33) The following set of data was obtained by the method of initial rates for the reaction:
2 HgCl2(aq) + C2O42-(aq) → 2 Cl–(aq) + 2 CO2(g) + Hg2Cl2(s)
What is the value of the rate constant, k?
A) 1.4 × 10-8 1/M2∙s
B) 1.3 × 10-7 1/M2∙s
C) 1.4 × 10-5 1/M2∙s
D) 1.3 × 10-4 1/M2∙s
34) The following set of data was obtained by the method of initial rates for the reaction:
(H3C)3CBr + OH– → (H3C)3COH + Br–
What is the order of reaction with respect to ion, OH–?
A) zero
B) first
C) second
D) none of these
35) The following set of data was obtained by the method of initial rates for the reaction:
(H3C)3CBr + OH– → (H3C)3COH + Br–
What is the value of the rate constant, k?
A) 8.8 × 10-4 s-1
B) 4.4 × 10-4 s-1
C) 1.8 × 10-4 s-1
D) none of these
36) The following set of data was obtained by the method of initial rates for the reaction:
BrO3–(aq) + 5 Br–(aq) + 6 H+(aq) → 3 Br2(aq) + 3 H2O(l).
What is the rate law for the reaction?
A) Rate = k[BrO3–][Br–][H+]4
B) Rate = k[BrO3–][Br–][H+]-4
C) Rate = k[BrO3–][Br–][H+]-2
D) Rate = k[BrO3–][Br–][H+]2
37) The following set of data was obtained by the method of initial rates for the reaction:
BrO3–(aq) + 5 Br–(aq) + 6 H+(aq) → 3 Br2(aq) + 3 H2O(l).
Calculate the initial rate when BrO3– is 0.30 M, Br– is 0.050 M, and H+ is 0.15 M.
A) 6.1 × 10-5 M/s
B) 2.7 × 10-3 M/s
C) 5.3 × 10-2 M/s
D) 8.4 × 10-2 M/s
38) The following set of data was obtained by the method of initial rates for the reaction:
S2O82-(aq) + 3 I–(aq) → 2 SO42-(aq) + I3–(aq)
What is the rate law for the reaction?
A) Rate = k[S2O82-][I–]
B) Rate = k[S2O82-][I–]5
C) Rate = k[S2O82-][I–]2
D) Rate = k[S2O82-]2[I–]
39) The following set of data was obtained by the method of initial rates for the reaction:
S2O82-(aq) + 3 I–(aq) → 2 SO42-(aq) + I3–(aq)
What is the initial rate when S2O82- is 0.15 M and I– is 0.15 M?
A) 4.10 × 10-6 M s-1
B) 8.10 × 10-3 M s-1
C) 1.22 × 10-2 M s-1
D) 5.40 × 10-2 M s-1
14
40) The first-order decomposition of hydrogen peroxide occurs according to the equation
2 H2O2(aq) → 2 H2O(l) + O2(g)
Using data from a concentration-time study of this reaction, which plot will produce a straight line?
A) [H2O2] versus time
B) [H2O2]2 versus time
C) 1/[H2O2] versus time
D) ln[H2O2] versus time
41) For a particular first-order reaction, it takes 48 minutes for the concentration of the reactant to
decrease to 25% of its initial value. What is the value for rate constant (in s-1) for the reaction?
A) 1.0 × 10-4 s-1
B) 4.8 × 10-4 s-1
C) 6.0 × 10-3 s-1
D) 2.9 × 10-2 s-1
42) The first-order reaction, SO2Cl2 → SO2 + Cl2, has a rate constant equal to 2.20 × 10-5 s-1 at
593 K. What percentage of the initial amount of SO2Cl2 will remain after 2.00 hours?
A) 1.00%
B) 14.7%
C) 17.1%
D) 85.4%
43) The first-order reaction, 2 N2O(g) → 2 N2(g) + O2(g), has a rate constant equal to 0.76 s-1 at
1000 K. How long will it take for the concentration of N2O to decrease to 42% of its initial
concentration?
A) 0.88 s
B) 1.1 s
C) 1.8 s
D) 2.4 s
44) The isomerization reaction, CH3NC → CH3CN, is first order and the rate constant is equal to
0.46 s-1 at 600 K. What is the concentration of CH3NC after 0.20 minutes if the initial concentration is
0.10 M?
A) 4.0 x 10-4 M
B) 9.1 x 10-4 M
C) 4.0 x 10-2 M
D) 9.1 x 10-2 M
45) The following reaction is first order: C2H6 → 2 CH3. If the rate constant is equal to 5.5 × 10-4 s-1
at 1000 K, how long will it take for 0.35 mol of C2H6 in a 1.00 L container to decrease to 0.10 mol in
the same container?
A) 7.6 min
B) 38 min
C) 106 min
D) 131 min
46) The decomposition of cyclopropane, was observed at 500°C and its concentration was monitored as
a function of time. The data set is given below. What is the order of the reaction with respect to
cyclopropane?
A) zero
B) first
C) second
D) third
47) The half life of the reaction shown below is found not to depend on the concentration of H2O2(aq).
2 H2O2(aq) → 2 H2O(l) + O2(g)
What is the order of this reaction?
A) zeroth
B) first
C) second
D) third
48) The rate constant, k, for a first-order reaction is equal to 4.2 × 10-4 s-1. What is the half-life for the
reaction?
A) 2.9 × 10-4 s
B) 1.2 × 103 s
C) 1.7 × 103 s
D) 2.4 × 103 s
49) Acetaldehyde decomposes at 750 K: CH3CHO → CO + CH4. The reaction is first order in
acetaldehyde and the half-life of the reaction is found to be 530 seconds. What is the rate constant for
the reaction at this temperature?
A) 2.7 x 10-3 s-1
B) 1.3 x 10-3 s-1
C) 2.7 x 102 s-1
D) 7.6 x 102 s-1
50) The first-order reaction, SO2Cl2 → SO2 + Cl2, has a half-life of 8.75 hours at 593 K. How long will
it take for the concentration of SO2Cl2 to fall to 12.5% of its initial value?
A) 0.165 hr
B) 3.22 hr
C) 6.06 hr
D) 26.2 hr
51) For the first-order reaction, 2 N2O(g) → 2 N2(g) + O2(g), what is the concentration of N2O after 3
half-lives if 0.15 mol of N2O is initially placed into in a 1.00-L reaction vessel?
A) 9.4 × 10-3 M
B) 1.9 × 10-2 M
C) 3.8 × 10-2 M
D) 7.5 × 10-2 M
52) The decay constant, k, is given for each of the beta emitters below. Which one has the shortest half
life?
A) 36Cl, 7.09 × 10-24 s-1
B) 131I, 9.94 × 10-7 s-1
C) 42K, 1.55 × 10-5 s-1
D) 63Ni, 2.39 × 10-10 s-1
53) Iodine-123, used in thyroid therapy, has a half-life of 13.27 hours. How many half-lives are required
for a 160 mg sample of iodine-123 to decay to 5.0 mg?
A) 0.031
B) 1.0
C) 5.0
D) 32
54) Neptunium-239 has a half-life of 2.35 days. How many days must elapse for a sample of 239Np to
decay to 1.00% of its original quantity?
A) 0.0640 days
B) 0.736 days
C) 1.36 days
D) 15.6 days
55) If a sample of 233Pa takes 62.7 days to decrease to 20.0% of its original mass, what is its half-life?
A) 0.0370 days
B) 27.0 days
C) 157 days
D) 195 days
56) What percentage of a radioactive substance remains after 6.00 half-lives have elapsed?
A) 0.78%
B) 1.56%
C) 3.31%
D) 6.25%
57) Fluorine-18 is a radioisotope widely used in positron emission tomography to investigate brain
activity. The half-life is 109.8 minutes. How long will it take for 2.75 μg of 18F to decay to 500 ng?
A) 0.288 min
B) 270 min
C) 871 min
D) 2.06 × 103 min
58) Fluorine-18 is an isotope used in Positron Emission Tomography (PET) to scan the brain. If a
researcher has 1.50 μg of 18F, how long before it decays to 1.0 ng? The half-life of 18F is 109.8
minutes.
A) 5.2 × 10-2 hr
B) 4.6 × 10-2 hr
C) 19 hr
D) 51 hr
59) What is the decay constant for a radioactive isotope which decreases to 34% of its original value in
2.48 hours?
A) 0.137 hr-1
B) 0.168 hr-1
C) 0.435 hr-1
D) 2.30 hr-1
60) An experiment with 55Co takes 47.5 hours. At the end of the experiment, 1.90 ng of 55Co remains.
If the half life is 18.0 hours, how many ng of 55Co were originally present?
A) 2.47 ng
B) 3.05 ng
C) 3.28 ng
D) 11.8 ng
61) A researcher needs 5.00 mg of 128Ba for an experiment. If the half-life of 128Ba is 2.43 days, how
many milligrams of 128BaCl2 must she order from the manufacturer if it takes 4.50 days to ship the
material from the manufacturer to the university? (Assume the molar mass of 128Ba is 128 g/mol.)
A) 11.6 mg
B) 18.0 mg
C) 21.5 mg
D) 44.9 mg
19
62) A plot of 1/[BrO–] vs time is linear for the reaction:
3 BrO–(aq) → BrO3–(aq) + 2 Br–(aq)
What is the order of the reaction with respect to the hypobromite ion, BrO–?
A) 0
B) 1
C) 2
D) 3
63) In aqueous solution, hypobromite ion, BrO–, reacts to produce bromate ion, BrO3–, and bromide ion,
Br–, according to the following chemical equation.
3 BrO–(aq) → BrO3–(aq) + 2 Br–(aq)
A plot of 1/[BrO–] vs. time is linear and the slope is equal to 0.056 M-1s-1. If the initial concentration of
BrO– is 0.80 M, how long will it take one-half of the BrO– ion to react?
A) 4.5 × 10-2 s
B) 7.1 s
C) 12 s
D) 22 s
64) The second-order reaction, 2 Mn(CO)5 → Mn2(CO)10 has a rate constant equal to 3.0 × 109 M-1s–
1 at 25°C. If the initial concentration of Mn(CO)5 is 1.0 × 10-5 M, how long will it take for 90.% of the
reactant to disappear?
A) 3.3 × 10-16 s
B) 3.7 × 10-15 s
C) 3.0 × 10-4 s
D) 3.0 × 103 s
65) Nitrogen dioxide decomposes at 300°C via a second-order process to produce nitrogen monoxide
and oxygen according to the following chemical equation.
2 NO2(g) → 2 NO(g) + O2(g).
A sample of NO2(g) is initially placed in a 2.50-L reaction vessel at 300°C. If the half-life and the rate
constant at 300°C are 11 seconds and 0.54 M-1 s-1, respectively, how many moles of NO2 were in the
original sample?
A) 0.17 mol
B) 0.42 mol
C) 5.9 mol
D) 15 mol
66) Hydrogen iodide decomposes at 800 K via a second-order process to produce hydrogen and iodine
according to the following chemical equation.
2 HI(g) → H2(g) + I2(g)
At 800 K it takes 142 seconds for the initial concentration of HI to decrease from 6.75 × 10-2 M to 3.50
× 10-2 M. What is the rate constant for the reaction at this temperature?
A) 5.12 × 10-4 M-1s-1
B) 9.69 × 10-2 M-1s-1
C) 10.3 M-1s-1
D) 1.95 × 103 M-1s-1
67) The reaction: 2 HI → H2 + I2, is second order and the rate constant at 800 K is 9.70 × 10-2 M-1 s-1.
How long will it take for 8.00 × 10-2 mol/L of HI to decrease to one-fourth of its initial concentration?
A) 0.619 s
B) 124 s
C) 387 s
D) 429 s
68) Which statement below regarding the half-life of a second-order reaction is true?
A) Each half-life is half as long as the preceding one.
B) Each half-life is twice as long as the preceding one.
C) Each half-life is four times as long as the preceding one.
D) The length of the half-life remains unchanged throughout the course of the reaction.
69) For the hypothetical second order reaction: A → products, the general rate law is: rate = k[A]2. How
long is the third half-life of the reaction if [A]0 is 0.080 M and the first half-life is 22 minutes?
A) 0.57 min
B) 1.7 min
C) 7.3 min
D) 88 min
70) If the units for rate are M s-1, what are the units for the rate constant, k, for a zeroth-order reaction?
A) s-1
B) M-1
C) M s-1
D) M-1 s-1
71) For the zeroth-order reaction: C → products, –Δ[C]/Δt = k, which of the following graphs would be
expected to give a straight line?