Question 1

When a catalyst is added to a reaction mixture, it

Accepted Answer

A)   increases the rate of collisions between reactant molecules.
B)   provides reactant molecules with more energy.
C)   slows down the rate of the back reaction.
D)   provides a new pathway (mechanism)  for the reaction.
E)   None of these choices are correct.F) B) and C)
G) A) and C)

Question 2

The kinetics of the decomposition of dinitrogen pentaoxide is studied at 50°C and at 75°C. Which of the following statements concerning the studies is correct?

Accepted Answer

A)   The rate at 75°C will be greater than the rate at 50°C because the activation energy will be lower at 75°C than at 50°C.
B)   The rate at 75°C will be greater than the rate at 50°C because the activation energy will be higher at 75°C than at 50°C.
C)   The rate at 75°C will be less than the rate at 50°C because the molecules at higher speeds do not interact as well as those at lower speeds.
D)   The rate at 75°C will be greater than at 50°C because the concentration of a gas increases with increasing temperature.
E)   The rate at 75°C will be greater than the rate at 50°C because the number of molecules with enough energy to react increases with increasing temperature.F) C) and E)
G) None of the above

Question 3

A rate constant obeys the Arrhenius equation, the factor A being 2.2 ×1013 s-1 and the activation energy being 150. kJ mol-1. What is the value of the rate constant at 227°C, in s-1?

Accepted Answer

A)   2.1 × 1013 s-1
B)   6.7 × 10-22 s-1
C)   1.5 × 1011 s-1
D)   4.7 × 10-3 s-1
E)   None of these choices are correct.F) C) and D)
G) None of the above

Question 4

The compound RX3 decomposes according to the equation 3RX3 → R + R2X3 + 3X2
In an experiment the following data were collected for the decomposition at 100°C. What is the average rate at which RX3 is disappearing over the entire experiment?
T(s)  [RX3](mol L-1) 
0 0.85
2 0.67
6 0.41
8 0.33
12 0.20
14 0.16

Accepted Answer

A)   0.011 mol L-1s-1
B)   0.019 mol L-1s-1
C)   0.044 mol L-1s-1
D)   0.049 mol L-1s-1
E)   0.069 mol L-1s-1F) None of the above
G) A) and E)

Question 5

Cyclopropane is converted to propene in a first-order process. The rate constant is 5.4 × 10-2 hr-1. If the initial concentration of cyclopropane is 0.150 M, what will its concentration be after 22.0 hours?

Accepted Answer

A)   0.0457 M
B)   0.105 M
C)   0.127 M
D)   0.492 M
E)   None of these choices are correct.F) C) and D)
G) A) and B)

Question 6

When the reaction A → B + C is studied, a plot 1/[A]t vs. time gives a straight line with a positive slope. What is the order of the reaction?

Accepted Answer

A)   Zero
B)   First
C)   Second
D)   Third
E)   More information is needed to determine the order.F) A) and E)
G) B) and D)

Question 7

Which one of the following sets of units is appropriate for a second-order rate constant?

Accepted Answer

A)   s-1
B)   mol L-1s-1
C)   L mol-1s-1
D)   mol2 L-2s-1
E)   L2 mol-2s-1F) D) and E)
G) C) and E)

Question 8

An elementary reaction is a simple, one-step process.

Accepted Answer

A) True 
 B)False

Question 9

The radioactive isotope tritium decays with a first-order rate constant k of 0.056 year-1. What fraction of the tritium initially in a sample is still present 30 years later?

Accepted Answer

A)   0.19
B)   0.60
C)   0.15
D)   2.8 × 10-38
E)   None of these choices are correct.F) C) and E)
G) A) and B)

Question 10

Which of the following affects the activation energy of a reaction?

Accepted Answer

A)   temperature of the reactants
B)   concentrations of reactants
C)   presence of a catalyst
D)   surface area of reactants
E)   reaction progressF) All of the above
G) D) and E)

Question 11

Which one of the following sets of units is appropriate for a third-order rate constant?

Accepted Answer

A)   s-1
B)   mol L-1s-1
C)   L mol-1s-1
D)   L2 mol-2s-1
E)   L3 mol-3s-1F) All of the above
G) A) and C)

Question 12

Which of the following sets of units could be appropriate for a zero-order rate constant?

Accepted Answer

A)   s-1
B)   L mol-1s-1
C)   L2 mol-2s-1
D)   L3 mol-3s-1
E)   mol L-1s-1F) A) and E)
G) A) and B)

Question 13

A reaction intermediate is a species corresponding to a local energy maximum on a reaction energy diagram.

Accepted Answer

A) True 
 B)False

Question 14

The gas-phase reaction CH3NC → CH3CN has been studied in a closed vessel, and the rate equation was found to be: Rate = -Δ[CH3NC]/Δt = k[CH3NC]. Which one of the following actions is least likely to cause a change in the rate of the reaction?

Accepted Answer

A)   lowering the temperature
B)   adding a catalyst
C)   using a larger initial amount of CH3NC in the same vessel
D)   using a bigger vessel, but the same initial amount of CH3NC
E)   continuously removing CH3CN as it is formedF) A) and B)
G) D) and E)

Question 15

The reaction X → Y is first-order overall and first-order with respect to the reactant X. The result of doubling the initial concentration of X will be to

Accepted Answer

A)   shorten the half-life of the reaction.
B)   increase the rate constant of the reaction.
C)   decrease the rate constant of the reaction.
D)   shorten the time taken to reach equilibrium.
E)   double the initial rate.F) D) and E)
G) B) and E)

Question 16

For the reaction 2A + B + 2C → D + E
The following initial rate data were collected at constant temperature. Determine the correct rate law for this reaction. All units are arbitrary.
Trial [A] [B] [C] Rate
1 0) 225 0.150 0.350 0.0217
2 0) 320 0.150 0.350 0.0439
3 0) 225 0.250 0.350 0.0362
4 0) 225 0.150 0.600 0.01270

Accepted Answer

A)   Rate = k[A][B][C]
B)   Rate = k[A]2[B][C]
C)   Rate = k[A]2[B][C]-1
D)   Rate = k[A][B]2[C] -1
E)   None of these choices are correct.F) B) and E)
G) C) and D)

Question 17

The reaction CH3NC(g)  → CH3CN(g)  is first-order with respect to methyl isocyanide, CH3NC. If it takes 10.3 minutes for exactly one quarter of the initial amount of methyl isocyanide to react, what is the rate constant in units of min-1 ?

Accepted Answer

A)   -0.135 min-1
B)   0.0279 min-1
C)   0.089 min-1
D)   0.135 min-1
E)   35.8 min-1F) B) and E)
G) None of the above

Question 18

The decomposition of SOCl2 is first-order in SOCl2. If the half-life for the reaction is 4.1 hr, how long would it take for the concentration of SOCl2 to drop from 0.36 M to 0.045 M?

Accepted Answer

A)   0.52 hr
B)   1.4 hr
C)   12 hr
D)   33 hr
E)   > 40 hrF) A) and E)
G) A) and B)

Question 19

A transition state is a species (or state) corresponding to an energy maximum on a reaction energy diagram.

Accepted Answer

A) True 
 B)False

Question 20

Tetrafluoroethylene, C2F4, can be converted to octafluorocyclobutane which can be used as a refrigerant or an aerosol propellant. A plot of 1/[C2F4] vs. time gives a straight line with a slope of 0.0448 L mol-1s-1. What is the rate law for this reaction?

Accepted Answer

A)   Rate = 0.0448 (L mol-1s-1) [C2F4]
B)   Rate = 22.3 (mol L-1s) [C2F4]
C)   Rate = 0.0448 (L mol-1s-1) [C2F4]2
D)   Rate = 22.3 (mol L-1s) [C2F4]2
E)   Rate = 0.0448 s-1 [C2F4]F) All of the above
G) D) and E)

Exam 16: Kinetics Rates and Mechanisms of Chemical Reactions

Which one of the following sets of units is appropriate for a second-order rate constant?

Correct Answer
verified

The decomposition of SOCl₂ is first-order in SOCl₂. If the half-life for the reaction is 4.1 hr, how long would it take for the concentration of SOCl₂ to drop from 0.36 M to 0.045 M?

Correct Answer
verified

Cyclopropane is converted to propene in a first-order process. The rate constant is 5.4 × 10^-2 hr^-1. If the initial concentration of cyclopropane is 0.150 M, what will its concentration be after 22.0 hours?

Correct Answer
verified

The radioactive isotope tritium decays with a first-order rate constant k of 0.056 year^-1. What fraction of the tritium initially in a sample is still present 30 years later?

Correct Answer
verified

When the reaction A → B + C is studied, a plot 1/[A]_t vs. time gives a straight line with a positive slope. What is the order of the reaction?

Correct Answer
verified

The kinetics of the decomposition of dinitrogen pentaoxide is studied at 50°C and at 75°C. Which of the following statements concerning the studies is correct?

Correct Answer
verified

Correct Answer
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Which of the following sets of units could be appropriate for a zero-order rate constant?

Correct Answer
verified

A reaction intermediate is a species corresponding to a local energy maximum on a reaction energy diagram.

Correct Answer
verified

The reaction X → Y is first-order overall and first-order with respect to the reactant X. The result of doubling the initial concentration of X will be to

Correct Answer
verified

When a catalyst is added to a reaction mixture, it

Correct Answer
verified

Which of the following affects the activation energy of a reaction?

Correct Answer
verified

An elementary reaction is a simple, one-step process.

Correct Answer
verified

Tetrafluoroethylene, C₂F₄, can be converted to octafluorocyclobutane which can be used as a refrigerant or an aerosol propellant. A plot of 1/[C₂F₄] vs. time gives a straight line with a slope of 0.0448 L mol^-1s^-1. What is the rate law for this reaction?

Correct Answer
verified

A rate constant obeys the Arrhenius equation, the factor A being 2.2 ×10¹³ s^-1 and the activation energy being 150. kJ mol^-1. What is the value of the rate constant at 227°C, in s^-1?

Correct Answer
verified

The reaction CH₃NC(g) → CH₃CN(g) is first-order with respect to methyl isocyanide, CH₃NC. If it takes 10.3 minutes for exactly one quarter of the initial amount of methyl isocyanide to react, what is the rate constant in units of min^-1 ?

Correct Answer
verified

Correct Answer
verified

Which one of the following sets of units is appropriate for a third-order rate constant?

Correct Answer
verified

A transition state is a species (or state) corresponding to an energy maximum on a reaction energy diagram.

Correct Answer
verified

The gas-phase reaction CH₃NC → CH₃CN has been studied in a closed vessel, and the rate equation was found to be: Rate = -Δ[CH₃NC]/Δt = k[CH₃NC]. Which one of the following actions is least likely to cause a change in the rate of the reaction?

Correct Answer
verified

Exam 16: Kinetics Rates and Mechanisms of Chemical Reactions

Which one of the following sets of units is appropriate for a second-order rate constant?

Correct AnswerverifiedShow Answer

The decomposition of SOCl2 is first-order in SOCl2. If the half-life for the reaction is 4.1 hr, how long would it take for the concentration of SOCl2 to drop from 0.36 M to 0.045 M?

Correct AnswerverifiedShow Answer

Cyclopropane is converted to propene in a first-order process. The rate constant is 5.4 × 10-2 hr-1. If the initial concentration of cyclopropane is 0.150 M, what will its concentration be after 22.0 hours?

Correct AnswerverifiedShow Answer

The radioactive isotope tritium decays with a first-order rate constant k of 0.056 year-1. What fraction of the tritium initially in a sample is still present 30 years later?

Correct AnswerverifiedShow Answer

When the reaction A → B + C is studied, a plot 1/[A]t vs. time gives a straight line with a positive slope. What is the order of the reaction?

Correct AnswerverifiedShow Answer

The kinetics of the decomposition of dinitrogen pentaoxide is studied at 50°C and at 75°C. Which of the following statements concerning the studies is correct?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Which of the following sets of units could be appropriate for a zero-order rate constant?

Correct AnswerverifiedShow Answer

A reaction intermediate is a species corresponding to a local energy maximum on a reaction energy diagram.

Correct AnswerverifiedShow Answer

The reaction X → Y is first-order overall and first-order with respect to the reactant X. The result of doubling the initial concentration of X will be to

Correct AnswerverifiedShow Answer

When a catalyst is added to a reaction mixture, it

Correct AnswerverifiedShow Answer

Which of the following affects the activation energy of a reaction?

Correct AnswerverifiedShow Answer

An elementary reaction is a simple, one-step process.

Correct AnswerverifiedShow Answer

Tetrafluoroethylene, C2F4, can be converted to octafluorocyclobutane which can be used as a refrigerant or an aerosol propellant. A plot of 1/[C2F4] vs. time gives a straight line with a slope of 0.0448 L mol-1s-1. What is the rate law for this reaction?

Correct AnswerverifiedShow Answer

A rate constant obeys the Arrhenius equation, the factor A being 2.2 ×1013 s-1 and the activation energy being 150. kJ mol-1. What is the value of the rate constant at 227°C, in s-1?

Correct AnswerverifiedShow Answer

The reaction CH3NC(g) → CH3CN(g) is first-order with respect to methyl isocyanide, CH3NC. If it takes 10.3 minutes for exactly one quarter of the initial amount of methyl isocyanide to react, what is the rate constant in units of min-1 ?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Which one of the following sets of units is appropriate for a third-order rate constant?

Correct AnswerverifiedShow Answer

A transition state is a species (or state) corresponding to an energy maximum on a reaction energy diagram.

Correct AnswerverifiedShow Answer

The gas-phase reaction CH3NC → CH3CN has been studied in a closed vessel, and the rate equation was found to be: Rate = -Δ[CH3NC]/Δt = k[CH3NC]. Which one of the following actions is least likely to cause a change in the rate of the reaction?

Correct AnswerverifiedShow Answer

Correct Answer
verified

The decomposition of SOCl₂ is first-order in SOCl₂. If the half-life for the reaction is 4.1 hr, how long would it take for the concentration of SOCl₂ to drop from 0.36 M to 0.045 M?

Correct Answer
verified

Cyclopropane is converted to propene in a first-order process. The rate constant is 5.4 × 10^-2 hr^-1. If the initial concentration of cyclopropane is 0.150 M, what will its concentration be after 22.0 hours?

Correct Answer
verified

The radioactive isotope tritium decays with a first-order rate constant k of 0.056 year^-1. What fraction of the tritium initially in a sample is still present 30 years later?

Correct Answer
verified

When the reaction A → B + C is studied, a plot 1/[A]_t vs. time gives a straight line with a positive slope. What is the order of the reaction?

Correct Answer
verified

Correct Answer
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Correct Answer
verified

Correct Answer
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Correct Answer
verified

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
verified

Tetrafluoroethylene, C₂F₄, can be converted to octafluorocyclobutane which can be used as a refrigerant or an aerosol propellant. A plot of 1/[C₂F₄] vs. time gives a straight line with a slope of 0.0448 L mol^-1s^-1. What is the rate law for this reaction?

Correct Answer
verified

A rate constant obeys the Arrhenius equation, the factor A being 2.2 ×10¹³ s^-1 and the activation energy being 150. kJ mol^-1. What is the value of the rate constant at 227°C, in s^-1?

Correct Answer
verified

The reaction CH₃NC(g) → CH₃CN(g) is first-order with respect to methyl isocyanide, CH₃NC. If it takes 10.3 minutes for exactly one quarter of the initial amount of methyl isocyanide to react, what is the rate constant in units of min^-1 ?

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

The gas-phase reaction CH₃NC → CH₃CN has been studied in a closed vessel, and the rate equation was found to be: Rate = -Δ[CH₃NC]/Δt = k[CH₃NC]. Which one of the following actions is least likely to cause a change in the rate of the reaction?

Correct Answer
verified