Deck 18: Chemical Kinetics

Question 1

The forward reaction AB → A + B is an example of a

A) Bimolecular decomposition
B) Unimolecular decomposition
C) Termolecular reaction
D) None of the above

Answer 1

B

Question 2

Which of the following will a catalyst affect?

A) Activation Energy
B) Enthalpy of Reaction
C) Final reaction concentrations
D) all of the above
E) none of the above

Answer 2

A

Question 3

Which of the following will an inhibitor affect?

A) Activation Energy
B) Rate constant
C) Reaction mechanism
D) All of the above
E) None of the above

Answer 3

D

Question 4

An uncatalyzed reaction has a DH of -44 kJ and the activation energy for the forward reaction is 21 kJ. What is the activation energy for the reverse reaction?

A) 21 kJ
B) 65 kJ
C) 44 kJ
D) 23 kJ

Question 5

Termolecular reactions are more likely to occur than

A) Unimolecular decompositions
B) Bimolecular reactions
C) All of the above
D) None of the above

Question 6

For a first order process, the product of the rate constant and the half life is

A) the rate
B) the molecularity
C) 1
D) ln 10
E) none of these

Question 7

The powers in the rate law are determined by

A) the coefficients of the balanced chemical equation.
B) the physical states of the reactants and products.
C) the principle of detailed balance.
D) experiment.
E) more that one of these are correct

Question 8

Reaction rates can change with

A) temperature.
B) the addition of a catalyst.
C) reactant concentrations.
D) all of these
E) none of these

Question 9

A certain first order reaction has a half life of 20.5 minutes. What is the value of the rate constant in s^-1.

A) 3.38×10^-2
B) 5.64×10^-4
C) 1.47×10^-2
D) 3.38×10^-4

Question 10

Exhibit 18-1
The following problem(s) pertain to the initial rate data given below for the reaction A₂ → 2A.
Refer to Exhibit 18-1. What is the order of the reaction?

A) 0
B) 1
C) 2
D) Not enough data to answer the question
E) None of the above

Question 11

Exhibit 18-1
The following problem(s) pertain to the initial rate data given below for the reaction A₂ → 2A.
Refer to Exhibit 18-1. What is the value of the rate constant?

A) .116
B) 11.6
C) 0.086
D) Not enough data to answer the question
E) None of the above

Question 12

Exhibit 18-1
The following problem(s) pertain to the initial rate data given below for the reaction A₂ → 2A.
Refer to Exhibit 18-1. What are the units for the rate constant?

A) s^-1
B) mol·L^-1·s^-1
C) L·mol^-1·s^-1
D) L²·mol^-2·s^-1
E) Not enough data to answer the question

Question 13

Exhibit 18-2
The following question(s) pertain to the initial rate data given below for the reaction:
Refer to Exhibit 18-2. What is the order of the reaction with respect to AB, B, and C?

A) 1,1,1
B) 2,1,1
C) 1,2,1
D) 1,1,2
E) 1,3,1

Question 14

Exhibit 18-2
The following question(s) pertain to the initial rate data given below for the reaction:
Refer to Exhibit 18-2. What is the overall order of the reaction?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 15

Exhibit 18-2
The following question(s) pertain to the initial rate data given below for the reaction:
Refer to Exhibit 18-2. What is the value of the rate constant?

A) 4
B) 3
C) 3.33
D) 18
E) None of the above

Question 16

Exhibit 18-2
The following question(s) pertain to the initial rate data given below for the reaction:
Refer to Exhibit 18-2. What are the units of the rate constant?

A) s^-1
B) mol·L^-1·s^-1
C) L·mol^-1·s^-1
D) L²·mol^-2·s^-1
E) L³·mol^-3·s^-1

Question 17

The rate constant for a first order reaction has the value of 1.25×10^-3s^-1. If the initial concentration of reactant is 2.5 mol·L^-1, what will be the molar concentration of the reactant after 5 minutes?

A) 2.31
B) 1.72
C) 2.49
D) 0.78
E) none of the above

Question 18

The rate constant for a second order reaction has the value of 2.5×10^-3 L·mol^-1·s^-1. If the initial concentration of reactant is 3.5 mol·L^-1, what will be the molar concentration of the reactant after 2.5 minutes?

A) 0.97
B) 1.5
C) 3.35
D) 2.33
E) none of the above

Question 19

Chloroethane decomposes at elevated temperatures according to the reaction
C₂H₅Cl(g) → C₂H₄(g) + HCl(g)
The reaction obeys first order kinetics. After 340 seconds at 800 K, a measurement shows that the concentration of C₂H₅Cl decreased from 0.0098 mol·L^-1 to 0.0016 mol·L^-1. What is the value of the rate constant at 800 K?

A) 7.4×10^-4
B) 2.3×10^-3
C) 2.0×10^-4
D) More data is needed to answer this question
E) none of the above

Question 20

Exhibit 18-3 The following question(s) pertain to the reaction of propene (C3CHCH2) with hydrochloric acid. A proposed mechanism for this chemical reaction is Refer to Exhibit 18-3. What is the predicted rate law for this mechanism?

A)

B) k₃[H₂Cl₂][CH₃CHClCH3^*]
C) k₂[HCl][CH₃CHCH₂]
D) none of the above

Question 21

Exhibit 18-3 The following question(s) pertain to the reaction of propene (C3CHCH2) with hydrochloric acid. A proposed mechanism for this chemical reaction is Refer to Exhibit 18-3. What would be the predicted rate law if the second step were the slow step? 

A)

B) k₂[H₂Cl₂][CH₃CHClCH₃^*]
C) k₂[HCl][CH₃CHCH₂]
D) none of the above

Question 22

Exhibit 18-3 The following question(s) pertain to the reaction of propene (C3CHCH2) with hydrochloric acid. A proposed mechanism for this chemical reaction is Refer to Exhibit 18-3. If the first step were the slow step, what would be the predicted order of the reaction with respect to propene?

A) 0
B) 1
C) 2
D) Experimental data required to answer this question
E) none of the above

Question 23

Exhibit 18-3 The following question(s) pertain to the reaction of propene (C3CHCH2) with hydrochloric acid. A proposed mechanism for this chemical reaction is Refer to Exhibit 18-3. Which of the species in the mechanism given above are reaction intermediates?

A) H₂Cl₂
B) HCl
C) CH₃CHClCH₃^*
D) a and b
E) none of the above

Question 24

Exhibit 18-4
The following question(s) pertain to the kinetic data given in the table below for the first order reaction:
Refer to Exhibit 18-4. What is the value of the rate constant in experiment 1?

A) 83
B) 0.012
C) 0.12
D) none of the above

Question 25

Exhibit 18-4
The following question(s) pertain to the kinetic data given in the table below for the first order reaction:
Refer to Exhibit 18-4. What is the value of the activation energy?

A) 10.2 kJ
B) 1.15 kJ
C) 14.4 kJ
D) not enough data to answer the question
E) none of the above

Question 26

Exhibit 18-4
The following question(s) pertain to the kinetic data given in the table below for the first order reaction:
Refer to Exhibit 18-4. What is the value of the pre-exponential term in the Arrhenius equation?

A) 1.2
B) 12
C) 0.012
D) not enough data to answer the question
E) none of the above

Question 27

Exhibit 18-4
The following question(s) pertain to the kinetic data given in the table below for the first order reaction:
Refer to Exhibit 18-4. What temperature is required to achieve the rate in experiment 3?

A) 154°C
B) 212°C
C) 245°C
D) 312°C
E) none of the above

Question 28

Exhibit 18-5
The following question(s) pertain to the scenario below.
A student performed a kinetic study of the reaction:
2NO(g) + O₂(g) → 2NO₂(g)
The student prepared the four plots seen below in lab, but forgot to label the axes. A classmate later told him that the reaction was second order in NO and first order in O₂. Not wanting to get a bad grade in the class, the student sets out to label the axes on the graphs. Refer to Exhibit 18-5. Which graph corresponds to plotting ln[NO] vs. time?

A) top left
B) top right
C) bottom left
D) bottom right
E) none of the above

Question 29

Exhibit 18-5
The following question(s) pertain to the scenario below.
A student performed a kinetic study of the reaction:
2NO(g) + O₂(g) → 2NO₂(g)
The student prepared the four plots seen below in lab, but forgot to label the axes. A classmate later told him that the reaction was second order in NO and first order in O₂. Not wanting to get a bad grade in the class, the student sets out to label the axes on the graphs. Refer to Exhibit 18-5. Which graph corresponds to plotting ln[O₂] vs. time?

A) top left
B) top right
C) bottom left
D) bottom right
E) none of the above

Question 30

Exhibit 18-5
The following question(s) pertain to the scenario below.
A student performed a kinetic study of the reaction:
2NO(g) + O₂(g) → 2NO₂(g)
The student prepared the four plots seen below in lab, but forgot to label the axes. A classmate later told him that the reaction was second order in NO and first order in O₂. Not wanting to get a bad grade in the class, the student sets out to label the axes on the graphs. Refer to Exhibit 18-5. Which graph corresponds to plotting 1/[NO] vs. time?

A) top left
B) top right
C) bottom left
D) bottom right
E) none of the above

Question 31

The collision rate per unit volume in a mixture increases with

A) the collision cross section
B) the mass of the molecules
C) the concentration
D) B and C
E) A and C

Question 32

For two colliding molecules with respective radii r₁ and r₂, the impact parameter, b, will always be

A) greater than the smaller of the two radii
B) greater than the larger of the two radii
C) equal to the sum of the two radii
D) greater than the sum of the two radii
E) less than the sum of the two radii

Question 33

Rate constants depend on

A) the collision cross section
B) the relative speed and orientation of impact
C) the probability that a collision will have sufficient energy to cause a reaction
D) All of the above
E) only B and C