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Test Bank General Chemistry, 10th edition 32
89. The Arrhenius equation, expresses the dependence of the rate constant on the
reaction temperature. The slope of a plot of ln(k) versus 1/T is equal to
A)
B)
C)
D)
E)
90. The rate constant for a reaction at 40.0°C is exactly 2 times that at 20.0°C. Calculate the
Arrhenius energy of activation for the reaction.
A)
2.00 kJ/mol
B)
3.18 kJ/mol
C)
26.4 kJ/mol
D)
5.8 kJ/mol
E)
none of these
91. Which of the following statements is not a requirement for a valid reaction mechanism?
A)
Each elementary reaction must be bimolecular.
B)
There must not be net production of any intermediates.
C)
The elementary reactions of a mechanism must add up to the net chemical
reaction.
D)
A mechanism must have only one rate-determining step.
E)
The rate law predicted by a mechanism must agree with the experimental rate law.
92. The decomposition of ozone may occur through the two-step mechanism shown below:
step 1
O3 → O2 + O
step 2
O3 + O → 2O2
The oxygen atom is considered to be a(n)
A)
activated complex.
B)
catalyst.
C)
reaction intermediate.
D)
product.
E)
reactant.
93. A proposed mechanism for the decomposition of N2O5 is as follows:
N2O5 NO2 + NO3
slow step
NO2 + NO3 NO2 + O2 + NO
fast step
NO + N2O5 3NO2
fast step
What is the overall chemical equation predicted by this mechanism?
A)
N2O5 + NO2 + NO3 → 4NO2 + O2
B)
N2O5 + NO → 3NO2
C)
2N2O5 → 4NO2 + O2
D)
N2O5 → NO2 + NO3
E)
N2O5 → NO2 + O2 + NO
94. A possible mechanism for the gas phase reaction of NO and H2 is as follows:
Step 1
2NO N2O2
Step 2
N2O2 + H2 N2O + H2O
Step 3
N2O + H2 N2 + H2O
Which of the following statements concerning this mechanism is not directly supported by
the information provided?
A)
Step 1 is the rate determining step.
B)
N2O2 is an intermediate.
C)
There is no catalyst in this reaction.
D)
The rate expression for step 1 is rate = k[NO]2.
E)
All steps are bimolecular reactions.
Test Bank General Chemistry, 10th edition 34
95. Determine the molecularity of the following elementary reaction: O3 → O2 + O.
A)
quadmolecular
B)
bimolecular
C)
unimolecular
D)
termolecular
E)
cannot be determined
96. For the elementary reaction A + B → C + D, what is the predicted rate law?
A)
Rate = k[A]2
B)
Rate = k[A][B]
C)
Rate = k
D)
Rate = k[B]2
E)
Rate = k[A]/[C]
MSC: general chemistry
97. Which of the following statements is incorrect?
A)
The slow step in a mechanism generally involves a three-body collision.
B)
After the addition of a catalyst, the collision rate between molecules is still the
same.
C)
Most collisions between reactant molecules do not lead to a product.
D)
Chemical reactions involve collisions between the participating molecules.
E)
A three-body collision is less likely than a two-body collision.
98. A proposed mechanism for the decomposition of N2O5 is as follows:
N2O5 NO2 + NO3
slow step
NO2 + NO3 NO2 + O2 + NO
fast step
NO + N2O5 3NO2
fast step
What is the rate law predicted by this mechanism?
A)
Rate = k1k2[N2O5][NO2][NO3]
B)
Rate = k2[NO2][NO3]
C)
Rate = k3[NO][N2O5]
D)
Rate = k1k2k3[N2O5]2
E)
Rate = k1[N2O5]
99. The complete mechanism for a reaction is considered to occur in two steps, one of which is
slow and the other fast:
A + 2B → C + D slow
A + C → E + F fast
What is the rate law predicted by this mechanism?
A)
Rate = k[A]2[B]
B)
Rate = k[A]2[B][C]
C)
Rate = k[A][C]
D)
Rate = k[A][B][C]
E)
Rate = k[A][B]2
100. The complete mechanism for a reaction is considered to occur in two steps, one of which is
slow and the other fast:
A + B → C + D slow
A + C → E + F fast
What is the net chemical equation predicted by this mechanism?
A)
2A + B → D + E + F
B)
A + C → E + F
C)
A + B → D + E + F
D)
A + B → C + D
E)
A + B + C → D + E + F
Test Bank General Chemistry, 10th edition 36
101. Below is a proposed mechanism for the decomposition of H2O2.
H2O2 + I– → H2O + IO–
slow
H2O2 + IO– → H2O + O2 + I–
fast
Which of the following statements is incorrect?
A)
IO– is a catalyst.
B)
I– is a catalyst.
C)
The net reaction is 2H2O2 → 2H2O + O2.
D)
The reaction is first-order with respect to [I–].
E)
The reaction is first-order with respect to [H2O2].
102. The acid-catalyzed reaction of acetone, CH3COCH3, with iodine can be represented by the
equation
CH3COCH3 + I2 CH2ICOCH3 + H+ + I–
It is found experimentally that the reaction is first-order with respect to both acetone and the
hydrogen ion. The rate of the reaction is independent of the iodine concentration. Which of
the following conclusions could be drawn from the experimental results?
1.
The uncatalyzed reaction would have a different pathway.
2.
Iodine is involved in the rate-determining step.
3.
The reaction takes place stepwise.
A)
1 only
B)
2 only
C)
3 only
D)
1 and 3
E)
1, 2, and 3
103. The following mechanism has been suggested for the reaction between nitrogen monoxide
and oxygen:
NO(g) + NO(g) → N2O2(g) (slow)
N2O2(g) + O2(g) → 2NO2(g) (fast)
Test Bank General Chemistry, 10th edition 37
According to this mechanism, the experimental rate law is
A)
second-order in NO and first-order in O2.
B)
second-order in NO and zero-order in O2.
C)
first-order in NO and first-order in O2.
D)
first-order in NO and second-order in O2.
E)
first-order in NO and zero-order in O2.
104. A mechanism that explains the rate law, Rate = k[(CH3)3CO2C(CH3)3], for the gas-phase
thermal decomposition of di-tert-butyl peroxide is given below.
For this proposed mechanism, the rate-determining step(s) must be
A)
step 1.
B)
step 3.
C)
step 2.
D)
step 1 + step 2 + step 3.
E)
2 times step 2.
105. The reaction CHCl3(g) + Cl2(g) CCl4(g) + HCl(g) has been proposed to occur by the
following mechanism.
Cl2 2Cl fast equilibrium
CHCl3 + Cl HCl + CCl3 slow step
CCl3 + Cl CCl4 fast
What is the rate law predicted by this mechanism?
A)
Rate = kexp[CHCl3][Cl2]
B)
Rate = k2[CHCl3][Cl]
C)
Rate = k1[Cl2]
D)
Rate = k3[CCl3][Cl]
E)
Rate = k2(k1/k-1)1/2[CHCl3][Cl2]1/2
Test Bank General Chemistry, 10th edition 38
106. Given the following fast equilibrium (below) proposed for the gas phase reaction between
NO and O2, what is the expression for the equilibrium concentration of the intermediate
NO3?
NO + O2 NO3
A)
B)
C)
D)
E)
107. One mechanism for the depletion of ozone in the stratosphere is proposed as follows:
Cl + O3 → ClO + O2
ClO + O → Cl + O2
Identify any catalysts and intermediates in the reaction.
A)
Cl is a catalyst, there are no intermediates
B)
O is an intermediate, ClO is a catalyst
C)
O2 is a catalyst, O is an intermediate
D)
ClO is a catalyst, there are no intermediates
E)
Cl is a catalyst, ClO is an intermediate
108. A suggested mechanism for the decomposition of ozone is as follows:
O3 O2 + O fast equilibrium
O + O3 2O2 slow step
Test Bank General Chemistry, 10th edition 39
What is the rate law predicted by this mechanism?
A)
Rate =
B)
Rate = k2[O] [O3]
C)
Rate =
D)
Rate =
E)
Rate =
109. 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)
II only
B)
III only
C)
I only
D)
two of these
E)
none of these
110. A suggested mechanism for the decomposition of ozone is
O3 O2 + O fast equilibrium
O + O3 2O2 slow step
When the concentration of ozone is doubled and the concentration of oxygen is doubled, the
instantaneous rate
A)
increases by a factor of 8.
B)
remains the same.
C)
increases by a factor of 4.
D)
decreases.
E)
increases by a factor of 2.
111. Which of the following statements is incorrect concerning a catalyst?
A)
A catalyst decreases the activation energy of a reaction.
B)
A catalyst may appear in the rate law for a reaction.
C)
A catalyst alters the equilibrium distribution of reactants and products.
D)
There is no net consumption of a catalyst in a reaction.
E)
A catalyst provides an alternative reaction mechanism.
112. The catalyzed pathway in a reaction mechanism has a __________ activation energy and
thus causes a __________ reaction rate.
A)
higher, lower
B)
higher, higher
C)
higher, steady
D)
lower, higher
E)
lower, steady
113. In a chemical reaction at constant temperature, the addition of a catalyst
A)
provides an alternative reaction pathway with a different activation energy.
B)
increases the concentration of the products at equilibrium.
C)
affects the equilibrium constant.
D)
increases the fraction of molecules with more than a given kinetic energy.
E)
decreases the energy released in the chemical reaction.
114. Which of the following reactions is not an example of homogeneous catalysis?
A)
2O3(g) 3O2(g)
B)
S2O82–(aq) + 2I–(aq) 2SO42–(aq) + I2(aq)
C)
2H2O2(aq) 2H2O(l) + O2(g)
D)
N2(g) + 3H2(g) 2NH3(g)
E)
CH3CO2CH3(aq) + H2O(l) CH3CO2H(aq) + CH3OH(aq)
115. Which of the following reactions is not an example of heterogeneous catalysis?
A)
CO(g) + 3H2(g) CH4(g) + H2O(g)
B)
C2H4(g) + H2(g) C2H6(g)
C)
2CO(g) + 2NO(g) 2CO2(g) + N2(g)
D)
2O3(g) 3O2(g)
E)
2SO2(g) + O2(g) 2SO3(g)
116. How many mechanistic steps are depicted by in this potential energy diagram for the
decomposition of cyclobutane to ethylene?
A)
two steps
B)
one step
C)
three steps
D)
four steps
E)
five steps
