68. The reaction is known to be zero order in A with a rate constant of 5.0 10–2
mol/L s at 25°C. An experiment was run at 25°C where [A]0 = M. The half-life
for the reaction is
A)
s
B)
s
C)
s
D)
s
E)
none of these
69. The reaction
exhibits the rate law
where k = 1.0 10–5 M–1 s–1 at 25°C. This reaction is run where the initial concentration of
NOBr ([NOBr]0) is 0.11 M. What is one half-life for this experiment?
A)
s
B)
s
C)
s
D)
s
E)
none of these
70. The reaction
exhibits the rate law
where k = 1.0 10–5 M–1 s–1 at 25°C. This reaction is run where the initial concentration of
NOBr ([NOBr]0) is 1.00 10–1 M.
The [NO] after 1.00 hour has passed is
A)
3.6 10–4 M
B)
9.9 10–3 M
C)
9.7 10–3 M
D)
1.0 10–3 M
E)
none of these
2.7 10−3
2.7 10−2
2.7 102
5.0 10−2
5.4 10−4
For the reaction A → Products, successive half-lives are observed to be 10.0 min and 40.0
min.
71. The reaction follows the integrated rate law
A)
B)
C)
D)
E)
none of these
72. At the beginning of the reaction, [A] was 0.71 M. The numerical value of the rate constant is
A)
0.069
B)
0.14
C)
10.
D)
0.036
E)
none of these
73. The reaction
is first order in N2O5. For this reaction at 45oC, the rate constant k = 1.0 10–5 s–1, where the
rate law is defined as
For a particular experiment ([N2O5]0 = 1.0 10–3 M), calculate [N2O5] after 3.5 105
seconds.
A)
3.5 M
B)
1.0 10–3 M
C)
3.0 10–5 M
D)
0 M
E)
10 M
Consider the reaction 3A + B + C → D + E where the rate law is defined as
.
An experiment is carried out where [B]0 = [C]0 = 1.00 M and [A]0 = 1.00 10–4 M.
74. After 3.00 minutes, [A] = 3.26 10–5 M. The value of k is
A)
6.23 10–3 L3/mol3·s
B)
3.26 10–5 L3/mol3·s
C)
1.15 102 L3/mol3·s
D)
1.00 108 L3/mol3·s
E)
none of these
75. The half-life for this experiment is
A)
1.11 102 s
B)
87.0 s
C)
6.03 10–3 s
D)
117 s
E)
none of these
76. The concentration of C after 10.0 minutes is
A)
1.00 M
B)
1.10 10–5 M
C)
0.330 M
D)
0.100 M
E)
none of these
77. The concentration of A after 10.0 minutes is
A)
1.06 10–9 M
B)
2.38 10–6 M
C)
9.80 10–6 M
D)
1.27 10–5 M
E)
none of these
78. The reaction
is second order in A. When [A]0 = 0.100 M, the reaction is 20.0% complete in 35.9 minutes.
Calculate the value of the rate constant (in L/min·mol).
A)
6.96 10–2
B)
5.57 10–4
C)
1.57
D)
1.11
E)
none of these
79. The reaction
is second order in A. When [A]0 = 0.100 M, the reaction is 20.0% complete in 43.2 minutes.
Calculate the half-life for the reaction.
A)
1.73 102 min
B)
10.8 min
C)
2.16 104 min
D)
7.68 min
E)
none of these
80. A first-order reaction is 40.0% complete at the end of 48.1 minutes. What is the value of the
rate constant (in min–1)?
A)
1.90 10–2
B)
1.06 10–2
C)
94.2
D)
52.5
E)
none of these
81. The OH· radical disproportionates according to the elementary chemical reaction
This reaction is second order in OH·. The rate constant for the
reaction is 2.0 10–12 cm3/molecules at room temperature. If the initial OH concentration is
1.3 1013 molecules/cm3, what is the first half-life for the reaction?
3.5 1011 s
B)
2.6 101 s
C)
3.8 10–2 s
D)
7.7 10–14 s
E)
1.9 10–2 s
82. At a particular temperature, N2O5 decomposes according to a first-order rate law with a half-
life of 3.0 s. If the initial concentration of N2O5 is 1.0 1016 molecules/cm3, what will be the
concentration in molecules/cm3 after 16.1 s?
A)
2.4 1014
B)
3.3 101
C)
1.0 1016
D)
1.4 1014
E)
2.3 10–1
83. At a given temperature, a first-order reaction has a rate constant of 3.4 10–3 s–1. The time
required for the reaction to be 44% completed is
A)
4.0 min
B)
1.2 min
C)
20 min
D)
2.8 min
E)
19 min
84. A chemical reaction that is first order in X is observed to have a rate constant of 1.7 10–2s–
1. If the initial concentration of X is 1.0 M, what is the concentration of X after 190 s?
A)
25 M
B)
0.68 M
C)
0.24 M
D)
0.96 M
E)
0.040 M
85. A particular first-order reaction has a rate constant of 0.0107 s–1. What is the half-life for
this reaction?
A)
1.00 s
B)
64.6 s
C)
93.2 s
D)
0.0155 s
E)
0.0107 s
86. The reaction A → products is first order. If the initial concentration of A is 0.528 M and,
after 16.3 seconds have elapsed, the concentration of A has fallen to 0.0122 M, what is the
rate constant of the reaction?
A)
0.231 s–1
B)
0.0425 s–1
C)
0.0316 s–1
D)
4.91 s–1
E)
0.0613 s–1
87. The reaction A → products is second order. If the initial concentration of A is 0.436 M and,
after 52.8 seconds have elapsed, the concentration of A has fallen to 0.0476 M, what is the
rate constant of the reaction?
A)
0.0419 M–1 s–1
B)
0.354 M–1 s–1
C)
0.0131 M–1 s–1
D)
0.00736 M–1 s–1
E)
0.0189 M–1 s–1
88. The radioactive nuclide undergoes first-order decay with a half-life of 9.31 min. If a
quantity of is produced, what fraction remains after 82.5 seconds?
A)
0.113
B)
0.00215
C)
0.148
D)
0.903
E)
0.0973
89. 63Ni decays by a first-order process via the emission of a beta particle. The 63Ni isotope has
a half-life of 100. years. How long will it take for 67% of the nickel to undergo decay?
A)
58 years
B)
0.77 years
C)
69 years
D)
25 years
E)
160 years
Two isomers (A and B) of a given compound dimerize as follows:
Both processes are known to be second order in reactant, and k1 is known to be 0.25 L/mol·s
at 25°C, where
In a particular experiment, A and B were placed in separate containers at 25°, where
[A]0 = 1.0 10–2 M and [B]0 = 2.5 10–2 M. It was found that [A] = 3[B] after the reactions
progressed for 3.0 minutes.
90. Calculate the concentration of A2 after 3.0 minutes.
A)
2.8 10–22 M
B)
6.9 10–3 M
C)
3.1 10–3 M
D)
1.6 10–3 M
E)
none of these
91. Calculate the value of where
A)
2.2 L/mol·s
B)
0.75 L/mol·s
C)
1.9 L/mol·s
D)
0.21 L/mol·s
E)
none of these
92. Two isomers (A and B) of a given compound dimerize as follows:
Both processes are known to be second order in reactant, and k1 is known to be 0.24 L/mol s
at 25°C, where:
In a particular experiment, A and B were placed in separate containers at 25oC, where
[A]0 = 1.0 10–2 M and [B]0 = 2.5 10–2 M. It was found that [A] = 3[B] after the reactions
progressed for 3.0 minutes. Calculate the half-life for the reaction involving A.
A)
s
B)
s
C)
s
D)
s
E)
none of these
93. The decomposition of N2O5(g) to NO2(g) and O2(g) obeys first-order kinetics. Assuming the
form of the rate law is:
where k = 3.4 10–5 s–1 at 25°C, what is the initial rate of reaction at 25°C where
[N2O5]0 = 8.2 10–2 M?
A)
mol/L·s
B)
mol/L·s
C)
mol/L·s
D)
mol/L·s
E)
none of these
94. The decomposition of N2O5(g) to NO2(g) and O2(g) obeys first-order kinetics. Assuming the
form of the rate law is:
where k = 5.4 10–5 s–1 at 25°C, what is the half-life for the reaction described?
A)
s
B)
s
4.2 102
1.0 102
1.8 102
2.4 103
3.4 10−5
2.8 10−6
4.1 10−4
8.2 10−2
1.9 104
1.3 104
C)
s
D)
s
E)
none of these
95. Consider a reaction of the type aA → Products in which the rate law is found to be rate =
k[A]3 (yes, a termolecular reaction is improbable but possible). If the first half-life of the
reaction is found to be 40 seconds, what is the time for the second half-life?
A)
10 seconds
B)
20 seconds
C)
80 seconds
D)
160 seconds
E)
320 seconds
96. The reaction obeys the rate law:
at 500. K.
If the initial concentration of NO2 is 1.00 M, how long will it take for the [NO2] to decrease
to 35.8% of its initial value?
A)
45.9 s
B)
73 s
C)
128 s
D)
s
E)
cannot be determined from this data
97. If the reaction 2HI → H2 + I2 is second order, which of the following will yield a linear
plot?
A)
log [HI] vs time
B)
1/[HI] vs time
C)
[HI] vs time
D)
ln [HI] vs time
E)
None of these.
3.4 108
7.8 10−5
1.40 10−2
98. The reaction 3NO → N2O + NO2 is found to obey the rate law, Rate = k[NO]2. If the first
half-life of the reaction is found to be 2.0 s, what is the length of the fourth half-life?
A)
2.0 s
B)
4.0 s
C)
8.0 s
D)
12.0 s
E)
16.0 s
99. In 6 M HCl, the complex ion Ru(NH3)63+ decomposes to a variety of products. The reaction
is first order in Ru(NH3)63+ and has a half-life of 14 hours at 25°C. Under these conditions,
how long will it take for the [Ru(NH3)63+] to decrease to 23.5% of its initial value?
A)
5.4 hours
B)
9.7 hours
C)
3.3 hours
D)
14 hours
E)
29 hours
100. The elementary chemical reaction O + ClO → Cl + O2 is made pseudo-first order in oxygen
atoms by using a large excess of ClO radicals. The rate constant for the reaction is
2.7 cm3/molecules. If the initial concentration of ClO is 1.0 1011 molecules/cm3, how long
will it take for the oxygen atoms to decrease to 10.% of their initial concentration?
A)
1.2 s
B)
0.039 s
C)
0.26 s
D)
0.85 s
E)
2.6 s
101. Determine the molecularity of the following elementary reaction: O3 → O2 + O.
A)
unimolecular
B)
bimolecular
C)
termolecular
D)
quadmolecular
E)
molecularity cannot be determined
102. The decomposition of ozone may occur through the two-step mechanism shown:
The oxygen atom is considered to be a(n)
A)
reactant
B)
product
C)
catalyst
D)
reaction intermediate
E)
activated complex
103. The rate law for a reaction is found to be Rate = k[A]2[B]. Which of the following
mechanisms gives this rate law?
I.
A + B E (fast)
E + B → C + D (slow)
II.
A + B E (fast)
E + A → C + D (slow)
III.
A + A → E (slow).
E + B → C + D (fast)
A)
I
B)
II
C)
III
D)
two of these
E)
none of these
104. The experimental rate law for the decomposition of nitrous oxide (N2O) to N2 and O2 is
Rate = k[N2O]2. Two mechanisms are proposed:
I.
N2O → N2 + O
N2O + O → N2 + O2
II.
2N2O N4O2
N4O2 → 2N2 + O2
Which of the following could be a correct mechanism?
A)
Mechanism I, with the first step as the rate-determining step.
B)
Mechanism I, with the second step as the rate-determining step as long as the first
step is a fast equilibrium step.
C)
Mechanism II, with the second step as the rate-determining step if the first step is a
fast equilibrium step.
D)
None of the choices (A-C) could be correct.
E)
At least two of the above choices (A-C) could be correct.
105. Consider the reaction 2O3(g) → 3O2(g). The following mechanism is proposed:
O3 O2 + O
O3 + O → 2O2
If we assume the second step of the mechanism is the rate determining step and the first step
is a fast equilibrium step, which of the following rate laws is predicted by this mechanism?
A)
rate = k[O3]
B)
rate = k[O3]2[O2]
C)
rate = k[O3]2[O2]–1
D)
rate = k[O3]2
E)
none of these
106. Of what use is it to find a rate law for a reaction?
A)
We can use the rate law to directly determine coefficients in the balanced equation.
B)
From the rate law we can evaluate potential reaction mechanisms.
C)
The rate law gives us a good indication of the thermodynamic stability of the
products.
D)
The rate law can lead us to determine the equilibrium constant for the reaction.
E)
None of these.
The following questions refer to the reaction 2A2 + B2 → 2C. The following mechanism has
been proposed:
step 1 (very slow)
A2 + B2 → R + C
step 2 (slow)
A2 + R → C
107. What is the molecularity of step 2?
A)
unimolecular
B)
bimolecular
C)
termolecular
D)
quadmolecular
E)
molecularity cannot be determined
108. Which step is rate determining?
A)
both steps
B)
step 1
C)
step 2
D)
a step that is intermediate to step 1 and step 2
E)
none of these
109. According to collision theory, the activated complex that forms in step 1 could have which
of the following structures? (The dotted lines represent partial bonds.)
A)
B)
C)
D)
E)
110. According to the proposed mechanism, what should the overall rate law be?
A)
rate = k[A2]2
B)
rate = k[A2]
C)
rate = k[A2][B2]
D)
rate = k[A2][R]
E)
rate = k[R]2