Deck 14: Kinetics

Question 1

Which of the following experimental conditions describe a reaction which is kinetically controlled?

A) $\Delta$ G = +100 kJ/mol_rxn; there is no observable reaction when reactants are mixed.
B) $\Delta$ G = - 100 kJ/mol_rxn; there is no observable reaction when reactants are mixed.
C) $\Delta$ G = +100 kJ/mol_rxn; the reaction proceeds rapidly when reactants are mixed.
D) $\Delta$ G = - 100 kJ/mol_rxn; the reaction proceeds rapidly when reactants are mixed.
E) These conditions do not describe kinetic control.

Answer 1

$\Delta$ G = - 100 kJ/mol_rxn; there is no observable reaction when reactants are mixed.

Question 2

Use the following table to determine the average rate during the period 800 to 1200 seconds for the decomposition of H₂O₂.

A) 8.0 x 10 ^{- 4} M/sec
B) 8.2 x 10 ^{- 4} M/s
C) 1.2 x 10 ^{- 3} M/s
D) 1.6 x 10 ^{- 3} M/s
E) 2.4 x 10 ^{- 3} M/s

Answer 2

8.0 x 10 ^{- 4} M/sec

Question 3

Determine the units for the rate constant, k, in the following rate expression: rate = k(A)²(B).

A) s ^{- 1}
B) M/s
C) M²/s
D) M³/s
E) M ^{- 2} s ^{- 1}

Answer 3

M ^{- 2} s ^{- 1}

Question 4

What will be the units of the rate constant, k, for the following reaction?
2 NO(g) + 2 H₂(g) $\rightarrow$ N₂(g) + 2 H₂O(g)   rate = k (NO)²(H₂)

A) s ^{- 1}
B) M/s
C) M ^{- 1} s ^{- 1}
D) M ^{- 2} s ^{- 1}
E) M² s ^{- 1}

Question 5

The disproportionation of NO to N₂O and NO₂ is third order in NO.
3 NO(g) F $\rightarrow$ N₂O(g) + NO₂(g)   rate = k (NO)³
What are the units for the rate constant, k?

A) M³/s
B) M²/s²
C) M ^{- 3} s ^{- 1}
D) M ^{- 2} s ^{- 2}
E) none of these

Question 6

Nitrogen reacts with hydrogen to form ammonia by the following reaction:
N₂(g) + 3 H₂(g) $\rightarrow$ 2 NH₃(g)
If the rate of consumption of hydrogen is 0.060 M/s, what is the rate at which N₂ is consumed?

A) 0.010 M/s
B) 0.020 M/s
C) 0.030 M/s
D) 0.060 M/s
E) 0.180 M/s

Question 7

Which equation describes the relationship between the rates at which NO is consumed and N₂ is produced in the following reaction?
2 NO(g) + 2 H₂(g) $\rightarrow$ N₂(g) + 2 H₂O(g)

A) rate N₂ = rate NO
B) rate N₂ = 2(rate NO)
C) 2(rate N₂) = rate NO
D) (rate N₂)² = rate NO
E) rate N₂ = (rate NO)²

Question 8

The reaction 2A $\rightarrow$ B is second order with respect to A. If the concentration of A is decreased by half, what will happen to the rate of the reaction?

A) The rate will double.
B) The rate will decrease by half.
C) The rate will remain constant.
D) The rate will increase by ln(A).
E) The rate will decrease by a factor of 4.

Question 9

For the reaction
3 N₂O(g) + C₂H₂(g) $\rightarrow$ 3 N₂(g) + 2 CO(g) + H₂O(g)
If water is produced at the rate of 0.10 M/s, what is the rate of production of N₂?

A) 0.10 M/s
B) 0.033 M/s
C) 0.30 M/s
D) 0.20 M/s
E) none of these

Question 10

Which of the following equations correctly describes the relationship between the instantaneous rate at which NO₂ and Cl₂ are consumed in the following reaction?
2 NO₂(g) + Cl₂(g) $\rightarrow$ 2 NO₂Cl(g)

A) -d(NO₂)/dt = 1/2 [-d(Cl₂)/dt]
B) -d(NO₂)/dt = 1/2 [d(Cl₂)/dt]
C) -d(NO₂)/dt = -d(Cl₂)/dt
D) -d(NO₂)/dt = 2 [-d(Cl₂)/dt]
E) -d(NO₂)/dt = 2 [d(Cl₂)/dt]

Question 11

In the following reaction
2 VO₄^3-(aq) + 3 Zn(s) + 16 H⁺(aq) $\rightarrow$ 2 V²⁺(aq) + 3 Zn²⁺(aq) + 8 H₂O(l)
The initial rate of disappearance of VO₄^3- was found to be 0.56 M/s. What is the initial rate of appearance of Zn²⁺?

A) -0.56 M/s
B) 0.37 M/s
C) 0.56 M/s
D) 0.84 M/s
E) 1.12 M/s

Question 12

The instantaneous rate of appearance of water from the reaction
4 NH₃(g) + 5 O₂(g) $\rightarrow$ 4 NO(g) + 6 H₂O(g)
At some moment in time is 21.3 mmHg/min. What is the instantaneous rate of disappearance of NH₃ at the same moment in time?

A) 10.7 mmHg/min
B) 14.2 mmHg/min
C) 21.3 mmHg/min
D) 32.0 mmHg/min
E) none of these

Question 13

When NH₃ is treated with O₂ at elevated temperatures, the rate of disappearance of NH₃ is found to be 3.5 x 10^-2 M s^-1. The equation for the reaction is
4 NH₃(g) + 5 O₂(g) $\rightarrow$ 4 NO(g) + 6 H₂O(g)
Calculate the rate of appearance of NO and H₂O.

Question 14

For which reactant or product in the following reaction will the rate of change of concentration with time be the largest?
6 Fe²⁺ + Cr₂O₇^2- + 14 H⁺ $\rightarrow$ 2 Cr³⁺ + 6 Fe³⁺ + 7 H₂O

A) Cr³⁺
B) Cr₂O₇^2-
C) Fe²⁺
D) H⁺
E) H₂O

Question 15

What is the correct rate law for the following reaction?
2 NO₂(g) + F₂(g) $\rightarrow$ 2 NO₂F(g)

A) rate = k_f(NO)²
B) rate = k_f(NO₂)²(F₂)
C) rate = -k_f(NO₂)²(F₂)
D) rate = -k_f(F₂)
E) Not enough information is available to determine the rate law.

Question 16

Which of the following affect whether a collision between molecules will result in a chemical reaction?

A) change in enthalpy for the reaction
B) orientation of the molecules
C) energy of the collision
D) 'b' and 'c' only
E) all of these

Question 17

Sum the following elementary steps in a mechanism to determine the stoichiometry of the overall reaction.
Cl₂(g) $\rightarrow$ 2Cl(g)
Cl(g) + CO(g) $\rightarrow$ COCl(g)
COCl(g) + Cl(g) $\rightarrow$ COCl₂(g)

A) Cl₂(g) + 2 CO(g) + 2 Cl(g) $\rightarrow$ 2 COCl₂(g)
B) 2 Cl₂(g) + CO(g) $\rightarrow$ COCl₂(g) + 2 Cl(g)
C) 2 Cl(g) + CO(g) $\rightarrow$ COCl₂(g)
D) Cl₂(g) + CO(g) + Cl(g) $\rightarrow$ COCl₂(g) + COCl(g)
E) none of these

Question 18

The reaction between chloroform (CHCl₃) and chlorine gas (Cl₂) proceeds by the following mechanism.
Cl₂ $\rightarrow$ 2 Cl
CHCl₃ + Cl $\rightarrow$ CCl₃ + HCl
CCl₃ + Cl $\rightarrow$ CCl₄
Which of the following substances are intermediates in the above mechanism?

A) Cl
B) CCl₃
C) CCl₄
D) HCl
E) Cl & CCl₃

Question 19

The overall rate of a chemical reaction is determined by

A) the fastest step in the reaction mechanism.
B) the first step in the reaction mechanism.
C) the slowest step in the reaction mechanism.
D) the last step in the reaction mechanism.
E) $\Delta$ G for the overall reaction.

Question 20

Which of the following rate laws suggests that the reaction probably occurs in a single step?

A)
B)
C)
D)

Question 21

Use the rate laws given below to determine which of the following reactions most likely occurs in a single step.

A)
B)
C)
D)
E)

Question 22

refer to the reaction:
NO(g) + O₃(g) $\rightarrow$ NO₂(g) + O₂(g)
for which the following rate data were obtained.


-The rate law for the reaction would be:

A) zero-order in NO
B) first-order in NO
C) second-order in NO
D) third-order in NO
E) none of the above

Question 23

refer to the reaction:
NO(g) + O₃(g) $\rightarrow$ NO₂(g) + O₂(g)
for which the following rate data were obtained.


-If these data were obtained by watching the rate at which NO disappears, what would be the initial instantaneous rate of disappearance of O₃ in
Trial 3?

A) 1.6 x 10^-5 M/s
B) 3.2 x 10^-5 M/s
C) 4.8 x 10^-5 M/s
D) 9.6 x 10^-5 M s
E) 14.4 x 10^-5 M/s

Question 24

refer to the reaction:
NO(g) + O₃(g) $\rightarrow$ NO₂(g) + O₂(g)
for which the following rate data were obtained.


-If a trial was run in which the initial (NO) was 3.15 x 10^-6 M and the initial (O₃) was 3.15 x 10^-6 M, the initial rate of reaction would be:

A) 1.6 x 10^-5 M/s
B) 3.2 x 10^-5 M/s
C) 3.6 x 10^-5 M/s
D) 4.8 x 10^-5 M/s
E) 7.2 x 10^-5 M/s

Question 25

This data applies to the next three problems.
The initial rate of disappearance of bromine (Br₂) for the reaction shown below was measured for several different concentrations of bromine, CH₃COCH₃, and H⁺ ions. (Note that H⁺ is a catalyst in this reaction - it participates in the reaction but is not itself consumed)


-The rate law for this reaction would be:

A) zero-order in H⁺ and first-order in Br₂
B) first-order in H⁺ and first-order in Br₂
C) first-order in H⁺ and zero-order in Br₂
D) second-order in H⁺ and zero-order in Br₂
E) none of the above.

Question 26

This data applies to the next three problems.
The initial rate of disappearance of bromine (Br₂) for the reaction shown below was measured for several different concentrations of bromine, CH₃COCH₃, and H⁺ ions. (Note that H⁺ is a catalyst in this reaction - it participates in the reaction but is not itself consumed)


-The rate law for this reaction would be:

A) zero-order in CH₃COCH₃
B) half-order in CH₃COCH₃
C) first-order in CH₃COCH₃
D) second-order in CH₃COCH₃
E) none of the above.

Question 27

This data applies to the next three problems.
The initial rate of disappearance of bromine (Br₂) for the reaction shown below was measured for several different concentrations of bromine, CH₃COCH₃, and H⁺ ions. (Note that H⁺ is a catalyst in this reaction - it participates in the reaction but is not itself consumed)


-The rate constant for this reaction is:

A) smaller than 1 x 10^-5
B) between 1 x 10^-5 and 1x 10^-4
C) between 1 x 10^-4 and 1 x 10^-3
D) between 1 x 10^-3 and 1
E) greater than 1

Question 28

The reaction shown below is first order in oxygen and second order in NO and has a rate constant of 7.1 x 10⁹ M^-2s^-1. What would the reaction rate be when the NO concentration is 0.0010 M and the O₂ concentration is 0.034 M?
2NO + O₂ $\rightarrow$ 2NO₂

A) 2.4 x 10⁵ M/s
B) 3.4 x 10^-8 M/s
C) 3.7 x 10³ M/s
D) 8.9 x 10^-5 M/s
E) 2.4 x 10² M/s

Question 29

The reaction following reaction was studied at 25 C, and the following experimental results were obtained.

Which 2 trials of experimental data should be chosen to find the order of the reaction with respect to S₂O₈²F1 ^- ?

A) trial 1 and 2
B) trial 2 and 3
C) trial 2 and 5
D) trial 1 and 3
E) none of these

Question 30

Use the following data on the initial rate of reaction to determine the overall order of the reaction.

A) first-order overall
B) second-order overall
C) third-order overall
D) fourth-order overall
E) none of these

Question 31

refer to the reaction for which the following data were obtained.
2 NO(g) + Br₂(g) $\rightarrow$ 2 NOBr(g)


-The rate law for this reaction would be:

A) zero-order in NO
B) half-order in NO
C) first-order in NO
D) second-order in NO
E) none of the above

Question 32

refer to the reaction for which the following data were obtained.
2 NO(g) + Br₂(g) $\rightarrow$ 2 NOBr(g)


-The rate law for this reaction would be:

A) zero-order in Br₂
B) half-order in Br₂
C) first-order in Br₂
D) second-order in Br₂
E) none of the above

Question 33

refer to the reaction for which the following data were obtained.
2 NO(g) + Br₂(g) $\rightarrow$ 2 NOBr(g)


-If these data were obtained by watching the rate at which NO disappears, what would be the initial instantaneous rate of disappearance of Br₂ in Trial 1?

A) 0.30 M/s
B) 0.60 M/s
C) 1.2 M/s
D) 2.4 M/s
E) 4.8 M/s

Question 34

refer to the reaction for which the following data were obtained.
2 NO(g) + Br₂(g) $\rightarrow$ 2 NOBr(g)


-The magnitude of the rate constant, k, for this reaction is:

A) less than 1 x 10^-4
B) between 10^-4 and 10^-2
C) between 0.01 and 100
D) between 100 and 10,000
E) more than 10,000

Question 35

refer to the reaction for which the following data were obtained.
2 NO(g) + Br₂(g) $\rightarrow$ 2 NOBr(g)


-A plot of (NO) versus time would most closely resemble:

A) a straight line with a positive slope.
B) a straight line with a negative slope.
C) a straight line with a slope of zero.
D) a curve in which the NO concentration increases rapidly at first and then slows down until eventually a maximum concentration is achieved.
E) a curve in which the NO concentration decreases rapidly at first and then slows down until eventually a minimum concentration is achieved.

Question 36

refer to the reaction
Cr₂O₇^2-(aq) + 6 I^-(aq) + 14 H⁺(aq) $\rightarrow$ 2 Cr³⁺(aq) + 3 I₂(aq) + 7 H₂O(l)
for which the following initial instantaneous rates of reaction were obtained.


-If the initial rate data are for the rate at which I^- disappears, -d(I^-)/dt, what would be the rate of disappearance of Cr₂O₇^2- in Trial 1?

A) 0.83 x 10^-4 M/s
B) 2.5 x 10^-4 M/s
C) 5 x 10^-4 M/s
D) 10 x 10^-4 M/s
E) 30 x 10^-4 M/s

Question 37

refer to the reaction
Cr₂O₇^2-(aq) + 6 I^-(aq) + 14 H⁺(aq) $\rightarrow$ 2 Cr³⁺(aq) + 3 I₂(aq) + 7 H₂O(l)
for which the following initial instantaneous rates of reaction were obtained.


-The rate law for this reaction would be:

A) zero-order in Cr₂O₇^2-
B) half-order in Cr₂O₇^2-
C) first-order in Cr₂O₇^2-
D) second-order in Cr₂O₇^2-
E) none of the above

Question 38

refer to the reaction
Cr₂O₇^2-(aq) + 6 I^-(aq) + 14 H⁺(aq) $\rightarrow$ 2 Cr³⁺(aq) + 3 I₂(aq) + 7 H₂O(l)
for which the following initial instantaneous rates of reaction were obtained.


-The rate law for this reaction would be:

A) first-order in both I^- and H⁺
B) first-order in I^- and second-order in H⁺
C) first-order in H⁺ and second-order in I^-
D) second-order in both H⁺ and I^-
E) none of the above

Question 39

refer to the reaction
Cr₂O₇^2-(aq) + 6 I^-(aq) + 14 H⁺(aq) $\rightarrow$ 2 Cr³⁺(aq) + 3 I₂(aq) + 7 H₂O(l)
for which the following initial instantaneous rates of reaction were obtained.


-The rate constant, k, for this reaction is:

A) less than 10^-6
B) between 10^-6 and 10^-3
C) between 10^-3 and 10³
D) between 10³ and 10⁶
E) more than 10⁶

Question 40

refer to the reaction
Cr₂O₇^2-(aq) + 6 I^-(aq) + 14 H⁺(aq) $\rightarrow$ 2 Cr³⁺(aq) + 3 I₂(aq) + 7 H₂O(l)
for which the following initial instantaneous rates of reaction were obtained.


-A graph of (Cr₂O₇^2-) versus time would most closely resemble

A) a straight line with a negative slope.
B) a straight line with a slope of zero.
C) a straight line with a positive slope.
D) a curve in which the Cr₂O₇^2- concentration decreases rapidly at first, and then the rate at which Cr₂O₇^2- disappears slows down with time.
E) a curve in which the Cr₂O₇^2- concentration increases rapidly at first, and then the rate at which Cr₂O₇^2- appears slows down with time.

Question 41

A certain substance, initially at 0.10 M in solution, decomposes by second-order kinetics. If the rate constant for this process is 0.40 M ^{- 1} min ^{- 1}, how much time in minutes is required for the concentration to reach 0.020 M?

A) 1.6 x 10 ^{- 4} min
B) 8.0 x 10 ^{- 3} min
C) 4.02 min
D) 50 min
E) 100 min

Question 42

The reaction A $\rightarrow$ C is found to be zero order. Which of the following will give a linear plot?

A) (A) vs. time
B) ln(A) vs. time
C) 1/(A) vs. time
D) None of these will be linear.

Question 43

The half-life for the first-order decomposition of nitramide, NH₂NO₂, into nitrous oxide, N₂O, and water is 123 min at 15°C.
NH₂NO₂ $\rightarrow$ N₂O + H₂O
What is the value of the rate constant (k) for this reaction?

Question 44

For the reaction in the above question, how long will it take in minutes for 2.0 g of nitramide to decompose until only 0.20 g remains?

Question 45

Which of the following graphs describes the relationship between rate and time for a first-order reaction?

A)
B)
C)
D)
E)

Question 46

Which plot best describe the rate of a second-order reaction?
2 A $\rightarrow$ B

A)
B)
C)
D)
E)

Question 47

A certain second-order reaction is found to have a rate constant of
0.135 M^-1 s^-1 What is the half-life of the reaction?

A) 5.1 s
B) 6.5 s
C) 7.4 s
D) none of these
E) impossible to determine from this information

Question 48

Which of the following statements about the half-life of a reaction is true?

A) The half-life doesn't depend on the order of the reaction.
B) The half-life of a first-order reaction increases with time.
C) The half-life of a second-order reaction is independent of concentration.
D) A zero-order reaction doesn't have a half-life.
E) None of the above are true.

Question 49

For a second-order reaction, it takes 15 seconds for the initial concentration of a reactant to decrease from 0.60 M to 0.53 M. What is the initial half-life of this reaction?

A) 47 s
B) 94 s
C) 114 s
D) 128 s
E) 228 s

Question 50

The rate constant, k, for the first-order decay of ¹⁴C is 1.21 x 10^-4 yr. If analysis of a piece of paper, parchment, or papyri suggests that 97.4% of the ¹⁴C that was present initially still remains in the sample, it would most likely be associated with which of the following battles?

A) Battle of Actium, 31 BC, Octavian defeating Mark Anthony
B) Battle of Hastings, 1066 AD, William of Normandy defeating King Harold II of England
C) Battle of Stirling Bridge, 1297 AD, William Wallace defeating John de Warrenne, Earl of Surrey
D) Battle of Yorktown, 1781 AD, Washington defeating Lord Cornwallis
E) Battle of Waterloo, 1815 AD, Wellington defeating Napoleon

Question 51

The decay of radioactive nuclei is a first-order kinetic process. Determine the half-life for the decay of ²³⁸U to ²⁰⁶Pb if the first-order rate constant is 4.87 x 10^-18 s^-1

A) 3.37 x 10^-18 s
B) 39.5 s
C) 1.42 x 10¹⁷ s
D) 4.11 x 10¹⁷ s
E) none of these

Question 52

The half-life of ²²⁸Ra is 1590 years. How long will it take for a sample of this nuclide to decay to 1.0% of its original activity?

A) 16 years
B) 1.6 x 10³ years
C) 4.1 x 10³ years
D) 1.1 x 10⁴ years
E) none of these

Question 53

The rate of a zero-order reaction

A) increases as reactant is consumed.
B) depends on the concentration of products.
C) decreases as reactant is consumed.
D) is independent of temperature.
E) is independent of the concentration of reactants and products.

Question 54

The reaction, N₂O₅ $\rightarrow$ NO₂ + 1/2 O₂, is first-order in N₂O₅ with a half-life of 19.25 min. How long would it take in minutes for the N₂O₅ concentration to decrease from 0.050 M to 0.030 M?

Question 55

The following data table should be used to answer
Reaction: A $\rightarrow$ B


-What is the rate constant, k, for this reaction?

A) 0.0175
B) 0.0560
C) 0.0815
D) 0.112
E) none of these

Question 56

The following data table should be used to answer
Reaction: A $\rightarrow$ B


-What is the half-life for this reaction, in seconds?

A) 29.1
B) 39.6
C) 47.3
D) 151
E) none of these

Question 57

The following data table should be used to answer
Reaction: A $\rightarrow$ B


-What will be the concentration of A when t = 120 seconds?

A) 0.047
B) 0.10
C) 0.13
D) 0.21
E) none of these

Question 58

If a plot of 1/[A] versus time produces a straight line, which of the following is true?

A) This reaction is first-order in A.
B) The reaction is second-order in A.
C) The reaction is first-order in two reactants.
D) The rate of reaction does not depend on the concentration of A.
E) none of the above

Question 59

Use the following data to answer
These data were obtained by monitoring the rate at which the OCl^- ion was consumed in the presence of a large excess of the I^- ion.
OCl^-(aq) + I^-(aq) $\rightarrow$ OI^-(aq) + Cl^-(aq)


-What is the rate constant (k) for this reaction?

A) between 10^-2 and 10^-1
B) larger than 10^-1 and smaller than 1
C) between 1 and 10
D) larger than 10 and smaller than 100
E) between 100 and 1000

Question 60

Use the following data to answer
These data were obtained by monitoring the rate at which the OCl^- ion was consumed in the presence of a large excess of the I^- ion.
OCl^-(aq) + I^-(aq) $\rightarrow$ OI^-(aq) + Cl^-(aq)


-What is the half-life in seconds?

A) between 0.01 and 0.1 seconds
B) between 0.1 and 1 second
C) between 1 and 10 seconds
D) between 10 and 100 seconds
E) none of the above

Question 61

Use the following data to answer
These data were obtained by monitoring the rate at which the OCl^- ion was consumed in the presence of a large excess of the I^- ion.
OCl^-(aq) + I^-(aq) $\rightarrow$ OI^-(aq) + Cl^-(aq)


-What is the concentration of OCl^- after 12 seconds?

A) between 1 x 10^-4 and 2 x 10^-4
B) between 2 x 10^-4 and 3 x 10^-4
C) between 3 x 10^-4 and 4 x 10^-4
D) between 4 x 10^-4 and 5 x 10^-4
E) between 5 x 10^-4 and 6 x 10^-4

Question 62

refer to the following reaction for the decomposition of H₂O₂.
2 H₂O₂(aq) $\rightarrow$ 2 H₂O(l) + O₂(g)
The following data were obtained


-The rate law for this reaction is:

A) zero-order in H₂O₂
B) first-order in H₂O₂
C) second-order in H₂O₂
D) third-order in H₂O₂
E) none of these

Question 63

refer to the following reaction for the decomposition of H₂O₂.
2 H₂O₂(aq) $\rightarrow$ 2 H₂O(l) + O₂(g)
The following data were obtained


-The half-life for this reaction is:

A) between 0 and 50 s
B) between 50 and 500 s
C) between 500 and 1500 s
D) between 1500 and 2000 s
E) the half-life can't be obtained from these data

Question 64

refer to the following reaction for the decomposition of H₂O₂.
2 H₂O₂(aq) $\rightarrow$ 2 H₂O(l) + O₂(g)
The following data were obtained


-What will be the H₂O₂ concentration after 4000 seconds?

A) less than 1.5 M
B) between 1.5 and 2.5 M
C) between 2.5 and 3.0 M
D) between 3.0 and 3.5 M
E) between 3.5 and 4.5 M

Question 65

refer to the reaction
2 N₂O₅(g) $\rightarrow$ 4 NO₂(g) + O₂(g)
for which the following data were obtained.


-The rate law for this reaction would be:

A) zero-order in N₂O₅
B) half-order in N₂O₅
C) first-order in N₂O₅
D) second-order in N₂O₅
E) none of the above

Question 66

refer to the reaction
2 N₂O₅(g) $\rightarrow$ 4 NO₂(g) + O₂(g)
for which the following data were obtained.


-The half-life for this reaction is:

A) between 0 and 12 s
B) between 12 and 120 s
C) between 120 and 1200 s
D) between 1200 and 12,000 s
E) between 12,000 and 120,000 s

Question 67

refer to the reaction
2 N₂O₅(g) $\rightarrow$ 4 NO₂(g) + O₂(g)
for which the following data were obtained.


-What will be the concentration of N₂O₅ after 5000 seconds?

A) between 0.001 and 0.010 M
B) between 0.010 and 0.10 M
C) between 0.10 and 0.4 M
D) between 0.4 and 0.8 M
E) between 0.8 and 1.2 M

Question 68

refer to the reaction
2 H₂O₂(aq)
2 H₂O(l) + O₂(g)
for which the following data were obtained at 25%C.


-The rate law for this reaction is

A) zero-order in hydrogen peroxide
B) half-order in hydrogen peroxide
C) first-order in hydrogen peroxide
D) second-order in hydrogen peroxide
E) none of the above

Question 69

refer to the reaction
2 H₂O₂(aq)
2 H₂O(l) + O₂(g)
for which the following data were obtained at 25%C.


-When will the concentration of H₂O₂ reach 0.010 M?

A) before 200 s
B) between 200 and 240 s
C) between 240 and 280 s
D) between 280 and 320 s
E) after 320 s

Question 70

H₂ and O₂ can react explosively. However, a mixture of H₂ and O₂ can exist indefinitely at room temperature with no reaction occurring. Explain why hydrogen and oxygen do not react under these conditions.

Question 71

If the rate constant increases from 0.40 M^-1 s^-1 at 25 C to 0.80 M^-1 s^-1 at 35 11ee9f13_6ea8_431e_9fac_3dff7a14c0f9_TB9692_11 C, what is the activation energy in kJ/mol for this reaction?

A) between 0 and 40 kJ mol
B) between 41 and 80 kJ/mol
C) between 81 and 120 kJ/mol
D) between 121 and 160 kJ/mol
E) between 161 and 200 kJ/mol

Question 72

A chemical reaction is found to be endothermic. Which of the following correctly describes the activation energy associated with the forward and the reverse reactions?

A) E_a forward = E_a reverse
B) E_a forward < E_a reverse at all temperatures
C) E_a forward > E_a reverse at all temperatures
D) E_a forward = E_a reverse at low temperatures
E) none of these

Question 73

The activation energy was measured for both the forward (E_a=150 kJ/mol_rxn) and reverse (E_a = 95 kJ/mol_rxn) directions of a reversible reaction. What would be the activation energy for the reverse reaction in the presence of a catalyst that decreased the activation energy for the forward reaction to
125 kJ/ mol_rxn?

A) 25 kJ/mol_rxn
B) 75 kJ/ mol_rxn
C) 120 kJ/ mol_rxn
D) 30 kJ/ mol_rxn
E) none of these

Question 74

Which of the following correctly describes the variation of rate constant, k_f, with temperature?

A) k_f = ln Z - E_a/RT
B) ln k_f = ln Z + e^-(Ea/RT)
C) ln k_f = ln Z - E_a/RT
D) ln k_f = ln Z + E_a/RT.
E) k_f = ln Z - E_a/RT.

Question 75

Which of the following plots represents the largest rate constant for an endothermic reaction?

A)

B)

C)

D)

E)

Question 76

For the gas phase decomposition of N₂O₂, k is 1.4 s ^{- 1} at 400 K and 43 s ^{- 1} at 450 K. What is the activation energy for this reaction?

A) 102 kJ/mol_rxn
B) 3.42 kJ/mol_rxn
C) 50.0 kJ/mol_rxn
D) 232 kJ/mol_rxn
E) 78.4 kJ/mol_rxn

Question 77

Which statement is true?

A) The rate of appearance of products of a chemical reaction is always equal to the rate of disappearance of reactants.
B) If a reaction follows a second-order rate law, it must have two steps in its reaction mechanism.
C) The half-life for a first-order reaction is always larger than the half-life for a second-order reaction.
D) The half-life for a first-order reaction is independent of the initial concentration of the reactant.
E) The half-life for a second-order reaction is independent of the initial concentration of the reactant.

Question 78

For the reaction, 2 NOCl(g) $\rightarrow$ 2 NO(g) + Cl₂(g),
The observed rate expression is rate = k(NOCl)². Which of the conditions listed below would cause a change in the value of the rate constant, k?

A) increase the concentration of NOCl
B) decrease the concentration of NOCl
C) decrease the concentration of NO
D) increase the temperature
E) increase the concentration of NOCl and decrease the concentration of NO and Cl₂

Question 79

As the reaction below proceeds, what happens (increase, decrease, or remain constant) to the rate of the forward reaction?
CO(g) + H₂O(g) $\rightarrow$ CO₂(g) + H₂(g)
As the reaction proceeds what happens to the rate of the reverse reaction (CO₂ + H₂ $\rightarrow$ CO + H₂O)?
Explain the above answers using the collision theory for gas-phase reactions.