49) 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
50) What is the minimum energy barrier that must be overcome for a chemical reaction to occur?
A) activation energy
B) net energy
C) potential energy
D) rate limiting energy
51) What factor affects the rate of a chemical reaction?
A) collision frequency
B) fraction of collisions with sufficient energy
C) orientation of molecules
D) All of these
52) A gas molecule at 298 K and 1 atm pressure undergoes a collision with another gas molecule
approximately every ________ seconds.
A) 10–15
B) 10-9
C) 10-6
D) 10-3
53) The fraction of collisions with sufficient energy to react is equal to
A) A.
B) Ea.
C) e-Ea/RT.
D) p.
54) When the temperature of a gas whose activation energy is 55 kJ/mol is increased from 300 K to 320 K,
the fraction of collisions with sufficient energy to react
A) decreases by a factor of 2.
B) decreases by a factor of 4.
C) increases by a factor of 2.
D) increases by a factor of 4.
55) A common rule in organic chemistry is that increasing the temperature of a reaction at room
temperature by 10°C doubles the rate. Calculate Ea for a reaction that follows this rule. Assume room
temperature is 25°C.
A) 0.576 kJ
B) 12.2 kJ
C) 38.4 kJ
D) 52.9 kJ
56) Consider a bimolecular reaction in the gas phase. Which one of the following changes in condition
will not cause an increase in the rate of the reaction?
A) add a catalyst
B) increase the temperature at constant volume
C) increase the volume at constant temperature
D) All of these will increase the rate of reaction.
57) Which part of the Arrhenius equation contains a term which measures the number of molecules that
have the correct orientation for reaction?
A) activation energy
B) e-Ea/RT
C) frequency factor
D) none of these
58) According to kinetic molecular theory, which of the following will decrease the rate of reaction?
A) increase the temperature
B) increase the concentration
C) increase the size of the molecule
D) increase the size of the reaction vessel
59) The reaction for the decomposition of dinitrogen monoxide gas to form oxygen radicals is:
. If the rate constant is 3.04 × 10-2 s-1 and the frequency factor is 8.00 × 1011 s-1,
what is the activation energy for the first-order reaction at 700°C?
A) 0.262 kJ/mol
B) 38.2 kJ/mol
C) 180 kJ/mol
D) 250 kJ/mol
60) The reaction for the decomposition of dinitrogen monoxide gas to form an oxygen radical is:
. If the activation energy is 250 kJ/mol and the frequency factor is 8.0 × 1011 s-1,
what is the rate constant for the first-order reaction at 1000 K?
A) 1.1 × 10-3 s-1
B) 7.0 × 10-2 s-1
C) 1.6 × 1013 s-1
D) 9.1 × 1024 s-1
61) The aquation of tris(1, 10-phenanthroline)iron(II) in acid solution takes place according to the
equation:
Fe(phen)32+ + 3 H3O+ + 3 H2O → Fe(H2O)62+ + 3 phenH+
If the activation energy is 126 kJ/mol and frequency factor is 8.62 × 1017 s-1, at what temperature is the
rate constant equal to 3.63 × 10-3 s-1 for the first-order reaction?
A) 0°C
B) 36°C
C) 50°C
D) 94°C
62) The aquation of tris(1, 10-phenanthroline)iron(II) in acid solution takes place according to the
equation:
Fe(phen)32+ + 3 H3O+ + 3 H2O → Fe(H2O)62+ + 3 phenH+
If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30°C is 9.8 × 10-3 min-1, what is the
frequency factor, A?
A) 2 × 10–24 min-1
B) 2 × 10–20 min-1
C) 5 × 1019 min-1
D) 5 × 1023 min-1
63) The aquation of tris(1, 10-phenanthroline)iron(II) in acid solution takes place according to the
equation:
Fe(phen)32+ + 3 H3O+ + 3 H2O → Fe(H2O)62+ + 3 phenH+
If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30°C is 9.8 × 10-3 min-1, what is the rate
constant at 50°C?
A) 4.4 × 10-4 min-1
B) 2.2 × 10-1 min-1
C) 4.6 × 100 min-1
D) 2.3 × 103 min-1
64) The first-order isomerization reaction: cyclopropane → propene, has a rate constant of 1.10 × 10–4 s-1
at 470°C and 5.70 × 10-4 s-1 at 500°C. What is the activation energy, Ea, for the reaction?
A) 46 kJ/mol
B) 110 kJ/mol
C) 260 kJ/mol
D) 380 kJ/mol
65) The first-order isomerization reaction: cyclopropane → propene, has a rate constant of 1.10 × 10–4 s -1
at 470°C and an activation energy of 264 kJ/mol. What is the temperature of the reaction when the rate
constant is equal to 4.36 × 10-3 s-1?
A) 126°C
B) 411°C
C) 510°C
D) 540°C
66) The elementary reaction representing the formation of ozone: O2(g) + O(g) + M(g) → O3(g) + M*(g) is
an example of a ________ reaction.
A) unimolecular
B) bimolecular
C) termolecular
D) tetramolecular
67) A mechanism for a naturally occurring reaction that destroys ozone is:
Step 1: O3(g) + HO(g) → HO2(g) + O2(g)
Step 2: HO2(g) + O(g) → HO(g) + O2(g)
Which species is an intermediate?
A) HO
B) HO2
C) O
D) O3
68) The decomposition of ozone in the stratosphere can occur by the following two-step mechanism:
Step 1: Br + O3 → BrO + O2
Step 2: BrO + O → Br + O2
Which species is an intermediate in this mechanism?
A) Br
B) BrO
C) O
D) O3
69) A mechanism for a naturally occurring reaction that destroys ozone is:
Step 1: O3(g) + HO(g) → HO2(g) + O2(g)
Step 2: HO2(g) + O(g) → HO(g) + O2(g)
What is the molecularity of the overall reaction?
A) unimolecular
B) bimolecular
C) none of these because molecularity is the difference of the exponents in the rate law
D) none of these because molecularity only refers to elementary steps
70) A suggested mechanism for the decomposition of peroxide (H2O2) is
H2O2 (aq) 2OH (aq)
H2O2 (aq) + OH (aq) H2O (l) + HO2 (g)
HO2 (g) + OH (aq) H2O (l) + O2 (g)
Which of the following correctly labels the chemical equation for the overall reaction and the reaction
intermediates?
A) Overall reaction = H2O2 (aq) H2O (l) + O2 (g), intermediates = HO2 (aq) + OH (aq)
B) Overall reaction = 3H2O2 (aq) 3H2O (l) + O2 (g), intermediates = OH (aq)
C) Overall reaction = 2H2O2 (aq) 2H2O (l) + O2 (g), intermediates = HO2 (aq) + OH (aq)
D) Overall reaction = H2O2 + 2OH (aq) + HO2 (aq) H2O (l) + 2OH (aq) + O2 (g) + HO2 (aq), intermediates
= HO2 (aq) + OH (aq)
71) Which of the following statements are true about reaction mechanisms?
I. A rate law can be written from the molecularity of the slowest elementary step.
II. The final rate law can include intermediates.
III. The rate of the reaction is dependent on the fastest step in the mechanism.
IV. A mechanism can never be proven to be the correct pathway for a reaction.
A) I, II, III
B) II, IV
C) I, III
D) I, IV
72) A three-step mechanism has been suggested for the formation of carbonyl chloride:
Step 1: Cl2→ 2 Cl (fast, equilibrium)
Step 2: Cl + CO → COCl (fast, equilibrium)
Step 3: COCl + Cl2 → COCl2 + Cl (slow)
What is the molecularity of the rate-determining step?
A) unimolecular
B) bimolecular
C) termolecular
D) none of these
73) When the concentration of A is doubled, the rate for the reaction: 2 A + B → 2 C quadruples.
When the concentration of B is doubled the rate remains the same. Which mechanism below is consistent
with the experimental observations?
A) Step 1: A + B ⇌ D (fast equilibrium)
Step 2: A + D → 2 C (slow)
B) Step 1: A + B → D (slow)
Step 2: A + D ⇌ 2 C (fast equilibrium)
C) Step 1: 2 A → D (slow)
Step 2: B + D → E (fast)
Step 3: E → 2 C (fast)
D) Step 1: 2 A ⇌ D (fast equilibrium)
Step 2: B + D → E (slow)
Step 3: E → 2 C (fast)
74) A mechanism for a naturally occurring reaction that destroys ozone is:
Step 1: O3(g) + HO(g) → HO2(g) + O2(g)
Step 2: HO2(g) + O(g) → HO(g) + O2(g)
Which species is a catalyst?
A) HO
B) HO2
C) O
D) O3
75) The decomposition of ozone in the stratosphere can occur by the following two-step mechanism:
Br + O3 → BrO + O2
BrO + O → Br + O2
Which species is a catalyst in this mechanism?
A) Br
B) BrO
C) O
D) O3
76) Which of the following does not affect the rate of a bimolecular reaction?
A) concentrations of reactants
B) presence of a catalyst
C) temperature
D) All of these affect the rate.
Shown is a concentration versus time plot for a reaction involving gases A, B, and C.
77) Which equation best represents the reaction?
A) 4A(g) → B(g) + 2C(g)
B) 4A(g) + B(g) → 2C(g)
C) 2C(g) → 4A(g) + B(g)
D) 2C(g) + B(g) → 4A(g)
78) Over the time interval 300 to 400 seconds, the rate of reaction with respect to A is Δ[A]/Δt = 3.7 × 10-5
M/s. Over the same time interval what is the rate of reaction with respect to B, Δ[B]/Δt?
A) Δ[B]/Δt = Δ[A]/Δt = 3.7 × 10-5 M/s
B) Δ[B]/Δt = (1/4)(Δ[A]/Δt) = (1/4)(3.7 × 10-5 M/s) = 9.2 × 10-6 M/s
C) Δ[B]/Δt = (1/2)(Δ[A]/Δt) = (1/2)(3.7 × 10-5 M/s) = 1.8 × 10-5 M/s
D) Δ[B]/Δt = -(1/2)(Δ[A]/Δt) = -(1/2)(3.7 × 10-5 M/s) = -1.8 × 10–5 M/s
79) Over the time interval 300 to 400 seconds, the rate of reaction with respect to A is Δ[A]/Δt = 3.7 × 10-5
M/s. Over the same time interval what is the rate of reaction with respect to C, Δ[C]/Δt?
A) Δ[C]/Δt = Δ[A]/Δt = 3.7 × 10-5 M/s
B) Δ[C]/Δt = (1/4)(Δ[A]/Δt) = (1/4)(3.7 × 10-5 M/s) = 9.2 × 10-6 M/s
C) Δ[C]/Δt = (1/2)(Δ[A]/Δt) = (1/2)(3.7 × 10–5 M/s) = 1.8 × 10-5 M/s
D) Δ[C]/Δt = –(1/2)(Δ[A]/Δt) = -(1/2)(3.7 × 10–5 M/s) = -1.8 × 10-5 M/s
80) Over the time interval 300 to 400 seconds, the rate of reaction with respect to A is Δ[A]/Δt = 3.7 × 10-5
M/s. What is the rate of reaction with respect to A over the time interval 700 to 800 seconds?
A) 0 M/s
B) less than 3.7 × 10-5 M/s
C) 3.7 × 10–5 M/s
D) greater than 3.7 × 10-5 M/s
81) Over the time interval 300 to 400 seconds, the rate of reaction with respect to A is Δ[A]/Δt = 3.7 × 10-5
M/s. What is the rate of reaction with respect to A over the time interval 0 to 100 seconds?
A) 0 M/s
B) less than 3.7 × 10-5 M/s
C) 3.7 × 10–5 M/s
D) greater than 3.7 × 10-5 M/s
The relative initial rates of the reaction A2 + B2 → products in vessels (a)-(d) are 1:1:4:4. Unshaded
spheres represent A2 molecules, and shaded spheres represent B2 molecules present at the beginning of
the reaction.
82) What is the order of reaction with respect to A2?
A) 0
B) 1
C) 2
D) 3
83) What is the order of reaction with respect to B2?
A) 0
B) 1
C) 2
D) 3
84) What is the overall order of reaction?
A) 0
B) 1
C) 2
D) 3
85) What is the rate law for this reaction?
A) Rate = k[A2]2
B) Rate = k[B2]2
C) Rate = k[A2][B2]
D) Rate = k[A2]2[B2]2
86) The following reaction is first order in A and first order in B:
A + B → Products Rate = k[A][B]
What is the initial rate of this reaction in vessel (b) relative to the initial rate of this reaction in vessel (a)?
Each vessel has the same volume. Shaded spheres represent A molecules, and unshaded spheres
represent B molecules present at the beginning of the reaction.
A) rate in vessel (b)/rate in vessel (a) = 1:2
B) rate in vessel (b)/rate in vessel (a) = 1:1
C) rate in vessel (b)/rate in vessel (a) = 2:1
D) rate in vessel (b)/rate in vessel (a) = 4:1
87) The following reaction is first order in A and first order in B:
A + B → Products Rate = k[A][B]
What is the initial rate of this reaction in vessel (b) relative to the initial rate of this reaction in vessel (a)?
Each vessel has the same volume. Shaded spheres represent A molecules, and unshaded spheres
represent B molecules present at the beginning of the reaction.
A) rate in vessel (b)/rate in vessel (a) = 1:2
B) rate in vessel (b)/rate in vessel (a) = 1:1
C) rate in vessel (b)/rate in vessel (a) = 2:1
D) rate in vessel (b)/rate in vessel (a) = 4:1
88) The following reaction is second order in A and first order in B:
A + B → Products Rate = k[A]2[B]
What is the initial rate of this reaction in vessel (b) relative to the initial rate of this reaction in vessel (a)?
Each vessel has the same volume. Shaded spheres represent A molecules, and unshaded spheres
represent B molecules present at the beginning of the reaction.
A) rate in vessel (b)/rate in vessel (a) = 1:2
B) rate in vessel (b)/rate in vessel (a) = 1:1
C) rate in vessel (b)/rate in vessel (a) = 2:1
D) rate in vessel (b)/rate in vessel (a) = 4:1
89) The following reaction is first order in A and first order in B:
A + B → Products Rate = k[A][B]
What is the rate constant k of this reaction in vessel (b) relative to the rate constant k of this reaction in
vessel (a)? Each vessel has the same volume. Shaded spheres represent A molecules, and unshaded
spheres represent B molecules.
A) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:2
B) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:1
C) rate constant k in vessel (b)/rate constant k in vessel (a) = 2:1
D) rate constant k in vessel (b)/rate constant k in vessel (a) = 4:1
90) The following reaction is first order in A and first order in B:
A + B → Products Rate = k[A][B]
What is the rate constant k of this reaction in vessel (b) relative to the rate constant k of this reaction in
vessel (a)? Each vessel has the same volume. Shaded spheres represent A molecules, and unshaded
spheres represent B molecules.
A) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:2
B) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:1
C) rate constant k in vessel (b)/rate constant k in vessel (a) = 2:1
D) rate constant k in vessel (b)/rate constant k in vessel (a) = 4:1
91) The following reaction is first order in A and first order in B:
A + B → Products Rate = k[A][B]
What is the rate constant k of this reaction in vessel (b) relative to the rate constant k of this reaction in
vessel (a)? Each vessel has the same volume. Shaded spheres represent A molecules, and unshaded
spheres represent B molecules.
A) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:2
B) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:1
C) rate constant k in vessel (b)/rate constant k in vessel (a) = 2:1
D) rate constant k in vessel (b)/rate constant k in vessel (a) = 4:1
92) The following reaction is second order in A and first order in B:
A + B → Products Rate = k[A]2[B]
What is the rate constant k of this reaction in vessel (b) relative to the rate constant k of this reaction in
vessel (a)? Each vessel has the same volume. Shaded spheres represent A molecules, and unshaded
spheres represent B molecules.
A) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:2
B) rate constant k in vessel (b)/rate constant k in vessel (a) = 1:1
C) rate constant k in vessel (b)/rate constant k in vessel (a) = 2:1
D) rate constant k in vessel (b)/rate constant k in vessel (a) = 4:1