Deck 15: Chemical Kinetics

Question 1

If the rate of reaction increases by a factor of 2.3 when the concentration of reactant increases by a factor of 1.5,the order of the reaction with respect to this reactant is

A)2.
B)1.
C)1.5.
D)4.
E)3.

Answer 1

2.

Question 2

The reaction 2NO(g)+ 2H₂(g) N₂(g)+ 2H₂O(g)
Is first order in H₂ and second order in NO.Starting with equal concentrations of H₂ and NO,the rate after 50% of the H₂ has reacted is what percent of the initial rate?

A)18.8%
B)37.5%
C)25.0%
D)50.0%
E)12.5%

Answer 2

12.5%

Question 3

Given: 2O₃(g) 3O₂(g)
Rate = k[O₃]²[O₂]^1
The overall order of the reaction and the order with respect to [O₃] are

A)(1 and 3.)
B)1 and 2.
C)0 and 1.
D)2 and 2.
E)3 and 2.

Answer 3

1 and 2.

Question 4

The reaction 2NO(g)+ 2H₂(g) N₂(g)+ 2H₂O(g)
Is first order in H₂ and second order in NO.Starting with equal concentrations of H₂ and NO,the rate after 25% of the H₂ has reacted is what percent of the initial rate?

A)75.0%
B)42.2%
C)6.25%
D)56.3%
E)1.56%

Question 5

If the rate of reaction increases by a factor of 9.6 when the concentration of reactant increases by a factor of 3.1,the order of the reaction with respect to this reactant is

A)1.5
B)3
C)4
D)2
E)1

Question 6

The concentrationtime dependence for a first-order reaction is: At which point on the curve is the reaction fastest?

A)A
B)B
C)C
D)A + t_½
E)The rates are the same at all points.

Question 7

If the average rate of formation of H₂(g)is 3.90 (mol H₂)L^1s^1 for the reaction 2PH₃(g) 2P(g)+ 3H₂(g),the unique average reaction rate is

A)3.90 molL^1s^1.
B)1.30 molL^1s^1.
C)2.60 molL^1s^1.
D)7.80 molL^1s^1.
E)11.7 molL^1s^1.

Question 8

If the average rate of decomposition of PH₃(g)is 3.2 (mol PH₃)L^1min^1 for the reaction 2PH₃(g) 2P(g)+ 3H₂(g),the unique average reaction rate is

A)3.2 molL^1min^1.
B)2.1 molL^1min^1.
C)1.6 molL^1min^1.
D)4.8 molL^1min^1.
E)6.4 molL^1min^1.

Question 9

Given: 4Fe²⁺(aq)+ O₂(aq)+ 2H₂O(l) 4Fe³⁺(aq)+ 4OH^(aq)
Rate = k[Fe²⁺][OH^]²[O₂]
The overall order of the reaction and the order with respect to O₂ are

A)4 and 1.
B)5 and 1.
C)3 and 1.
D)4 and 2.
E)7 and 1.

Question 10

If the rate of a reaction increases by a factor of 64 when the concentration of reactant increases by a factor of 4,the order of the reaction with respect to this reactant is

A)16.
B)2.
C)4.
D)1.
E)3.

Question 11

The concentrationtime dependence for two first order reactions is: Which reaction has the greater t_½?

Question 12

For the reaction S₂O₈2^(aq)+ 3I^(aq) 2SO₄2^(aq)+ I₃(aq),rate = k[S₂O₈2^][I^].When the reaction is followed under pseudo-first-order conditions with [S₂O₈2^] = 200 m M and [I^] = 1.5 m M,the rate constant was 1.82 s^1.The second order rate constant,k,for the reaction is

A)1.21  10³ M^1s^1.
B)6.07  10³ M^1s^1.
C)9.10 M^1s^1.
D)1.37  10^-2 M^1s^1.
E)1.82 M^1s^1.

Question 13

It is important to distinguish between the reaction rate and the rate constant.The units of reaction rate are M∙s^1.True or false?

Question 14

The rate of formation of oxygen in the reaction 2N₂O₅(g) 4NO₂(g)+ O₂(g)
Is 2.28 (mol O₂)L^1s^1.What is the rate of formation of NO₂?

A)0.57 (mol NO₂)L^1s^1
B)9.12 (mol NO₂)L^1s^1
C)2.28 (mol NO₂)L^1s^1
D)1.14 (mol NO₂)L^1s^1
E)4.56 (mol NO₂)L^1s^1

Question 15

The concentrationtime curves for two sets of reactions,A/B and C/D,are: Which of the reactions are first order?

A)B and D
B)A and B
C)C and D
D)A and C

Question 16

Given: 2A(g)+ B(g) C(g)+ D(g)
When [A] = [B] = 0.10 M,the rate is 2.0 Ms^1; for [A] = [B] = 0.20,the rate is 8.0 Ms^1; and for [A] = 0.10 M,[B] = 0.20 M,the rate is 2.0 Ms^1.The rate law is

A)rate = k[A].
B)rate = k[B]².
C)rate = k[A][B]⁰.
D)rate = k[A][B].
E)rate = k[A]².

Question 17

A first-order reaction has a rate constant of 0.00300 s^1.The time required for 60% reaction is

A)153 s.
B)73.9 s.
C)170 s.
D)133 s.
E)305 s.

Question 18

The concentrationtime curves for two sets of reactions,A/B and C/D,are: Which set of reactions has the largest rate constant?

Question 19

For a given first-order reaction,after 2.00 min,20% of the reactants remain.Calculate the rate constant for the reaction.

A)0.0134 s^1
B)0.000808 s^1
C)74.6 s^1
D)0.00582 s^1
E)0.00186 s^1

Question 20

The concentrationtime dependence is shown below for two first-order reactions is: Which reaction has the larger rate constant?

Question 21

Given: A  P rate = k[A] If 20% of A reacts in 5.12 min,calculate the time required for 90% of A to react.

A)52.8 min
B)1.05 min
C)2.42 min
D)3170 min
E)22.9 min

Question 22

For a second-order reaction,a straight line is obtained from a plot of

A)1/[A] vs t.
B)ln(1/t)vs [A].
C)[A] vs t.
D)ln[A] vs t.
E)ln(t)vs [A].

Question 23

A nonsteroidal anti-inflammatory drug is metabolized with a first-order rate constant of 3.25 day^1.What fraction of the drug remains in the body after 13.0 hr?

A)0.172
B)0.0174
C)0.828
D)0.873
E)0.127

Question 24

For the reaction cyclobutane(g) 2ethylene(g)at 800 K,a plot of ln[cyclobutane] vs t gives a straight line with a slope of 1.6 s^1.Calculate the time needed for the concentration of cyclobutane to fall to 1/16 of its initial value.

A)2.3 s
B)1.7 s
C)1.3 s
D)0.63 s
E)1.6 s

Question 25

A first-order reaction has a half-life of 1.10 s.If the initial concentration of reactant is 0.384 M,how long will it take for the reactant concentration to reach 0.00100 M?

A)9.45 s
B)0.106 s
C)4.10 s
D)1.52 s
E)0.244 s

Question 26

Technetium-99m,used to image the heart and brain,has a half-life of 6.00 h.What fraction of technetium-99m remains in the body after 1 day?

A)0.0625
B)0.250
C)0.0313
D)0.125

Question 27

For the reaction A  products,the following data were collected. Determine the order of the reaction and calculate the rate constant.

Question 28

For the reaction cyclopropane  propene
A plot of ln[cyclopropane] vs time in seconds gives a straight line with slope 4.1  10^3 s^1 at 550C.What is the rate constant for this reaction?

A)3.9  10^2 s^1
B)8.2  10^3 s^1
C)4.1  10^3 s^1
D)1.8  10^3 s^1
E)2.1  10^3 s^1

Question 29

A given first-order reaction has a rate constant of 0.00300 s^1.The time required for 85% reaction is

A)632 s.
B)23.5 s.
C)275 s.
D)316 s.
E)54.2 s.

Question 30

The rates of first-order and second-order reactions do not change with elapsed time.True or false?

Question 31

For a given first-order reaction,after 230 s,33% of the reactants remain.Calculate the rate constant for the reaction.

A)207 s^1
B)0.00174 s^1
C)0.00209 s^1
D)0.000756 s^1
E)0.00482 s^1

Question 32

What is the rate constant for a first-order reaction with a half-life of 9.0 ms?

A)13 s^1
B)77 s^1
C)9.0 s^1
D)6.2 s^1
E)0.11 s^1

Question 33

Consider the reaction 2N₂O(g) 2N₂(g)+ O₂(g)
Rate = k[N₂O]
For an initial concentration of N₂O of 0.50 M,what is the concentration of N₂O remaining after 2.0 min if k = 3.4  10^3 s^1?

A)0.50 M
B)0.55 M
C)0.66 M
D)0.33 M
E)0.17 M

Question 34

Consider the reaction 2N₂O₅(g) 4NO₂(g)+ O₂(g)
Rate = k[N₂O₅]
Calculate the time for the concentration of N₂O₅ to fall to one-fourth its initial value if the half-life is 133 s.

A)133 s
B)33.3 s
C)266 s
D)66.6 s
E)533 s

Question 35

For the reaction cyclopropane(g) propene(g)at 500C,a plot of ln[cyclopropane] vs t gives a straight line with a slope of 0.00067 s^1.What is the order of this reaction and what is the rate constant?

Question 36

Consider the reaction 2N₂O(g) 2N₂(g)+ O₂(g)
Rate = k[N₂O]
Calculate the time required for the concentration of N₂O(g)to decrease from 0.75 M to 0.33 M.The rate constant for the reaction is k = 6.8  10^3 s^1.

A)2.7 min
B)1.7 min
C)0.87 min
D)0.92 min
E)2.0 min

Question 37

A given compound decomposes with a half-life of 8.0 s and the half-life is independent of the concentration.How long does it take for the concentration to decrease to one-ninth of its initial value?

A)32 s
B)25 s
C)72 s
D)64 s
E)3.6 s

Question 38

The reaction 2ClO₂(g)+ F₂(g) 2FClO₂(g)
Is first order in both ClO₂ and F₂.When the initial concentrations of ClO₂ and F₂ are equal,the rate after 25% of the F₂ has reacted is what percent of the initial rate?

A)75.0%
B)18.8%
C)37.5%
D)28.1%
E)12.5%

Question 39

Consider the reaction 2N₂O₅(g) 4NO₂(g)+ O₂(g)
Rate = k[N₂O₅]
If the initial concentration of N₂O₅ is 0.80 M,the concentration after 5 half-lives is

A)0.11 M.
B)0.025 M.
C)0.032 M.
D)0.16 M.
E)0.050 M.

Question 40

What is the half-life of a reaction that has a rate constant of 280 s^1?

A)194 s
B)3.6 ms
C)404 ms
D)Because the concentration of reactant is not given, the calculation cannot be performed.
E)2.5 ms

Question 41

The activation energy of a reaction is given by

A)+(slope of a plot of lnk vs 1/T) R.
B)((slope of a plot of lnk vs 1/T) R.)
C)(R  (slope of a plot of lnk vs 1/T).)
D)+(slope of a plot of lnk vs 1/T) R.
E)((slope of a plot of lnk vs 1/T) R.)

Question 42

The rate law for the following mechanism is ClO^(aq)+ H₂O(l) HOCl(aq)+ OH^(aq)
K,fast
I^(aq)+ HOCl(aq) HOI(aq)+ Cl^(aq)
K₁,slow
HOI(aq)+ OH^(aq) OI^(aq)+ H₂O(l)
K₂,fast

A)rate = k₁[I^][HOCl].
B)rate = k₁K[ClO^][I^][OH^].
C)rate = k₁K[ClO^][I^][OH^]^1.
D)rate = k₁k₂K[ClO^][I^].
E)rate = k₁K[ClO^][I^].

Question 43

A reaction has k = 8.39 M^1s^1.How long does it take for the reactant concentration to drop from 0.0840 M to 0.0220 M?

A)5.42 s
B)2.00 s
C)1.42 s
D)8.39 s
E)4.00 s

Question 44

The reaction [(CN)₅CoOH₂]^2(aq)+ SCN^(aq) [(CN)₅CoSCN]^3 + H₂O(l)has the rate law,rate = k[(CN)₅CoOH₂2^].Postulate a mechanism for this reaction.

Question 45

A second-order reaction has a rate constant of 1.25 M^1s^1.If the initial reactant concentration is 1.0 M,calculate the time required for 90% reaction.

A)1.3 s
B)7.2 s
C)0.13 s
D)17 s
E)0.89 s

Question 46

Consider the reaction for the dimerization of butadiene(g)at a certain temperature.
2C₄H₆(g) C₈H₁₂(g) rate = k[C₄H₆]².
When the initial concentration of butadiene is 0.500 M,the time required for 80% dimerization is measured at 11.4 s.What is the rate constant for the dimerization?

Question 47

A reaction that has a very low activation energy

A)has a rate that is very sensitive to temperature.
B)has a rate that does not change much with temperature.
C)must be second order.
D)gives a curved Arrhenius plot.
E)must be first order.

Question 48

The reaction 2NO(g)+ O₂(g) 2NO₂(g)has H_r = 114 kJmol^1.A possible mechanism for this reaction is
2NO(g)b N₂O₂(g)
rapid equilibrium,K
N₂O₂(g)+ O₂(g) 2NO₂(g)
slow,k
Draw the reaction profile diagram (plot of energy vs reaction coordinate)for this reaction and label any intermediates and activated complexes.

Question 49

What is the half-life of a second order reaction?

Question 50

Consider the dimerization reaction below: 2A A₂
Rate = k[A]²
When the initial concentration of A is 2.0 M,it requires 30 min for 60% of A to react.Calculate the rate constant.

A)1.1  10^3 M^1s^1
B)3.2  10^4 M^1s^1
C)5.0  10^4 M^1s^1
D)1.9  10^4 M^1s^1
E)4.2  10^4 M^1s^1

Question 51

A certain reaction has a rate constant of 8.8 s^1 at 298 K and 140 s^1 at 323 K.What is the activation energy for this reaction?

A)38 kJmol^1
B)89 kJmol^1
C)120 kJmol^1
D)23 kJmol^1
E)1.2 kJmol^1

Question 52

The reaction profile for the reaction
[(CN)₅CoOH₂]^2(aq)+ SCN^(aq) [(CN)₅CoSCN]^3 + H₂O(l)
is Identify the structure of B.What do A and C represent?

Question 53

For the reaction HO(g)+ H₂(g) H₂O(g)+ H(g)
A plot of versus 1/T gives a straight line with a slope equal to 5.1  10³ K.What is the activation energy for the reaction?

A)42 kJmol^1
B)98 kJmol^1
C)0.61 kJmol^1
D)5.1 kJmol^1
E)12 kJmol^1

Question 54

Given: CH₄(g)+ Cl₂(g) CH₃Cl(g)+ HCl(g)
The rate law for this elementary process is

A)rate = k[Cl₂].
B)k[CH₃Cl][HCl].
C)rate = k[CH₄][Cl₂].
D)rate = k[CH₄].
E)rate = k[CH₄]².

Question 55

A catalyst facilitates a reaction by

A)increasing the activation energy for the reverse reaction.
B)lowering the activation energy of the reaction.
C)shifting the position of the equilibrium of the reaction.
D)decreasing the temperature at which the reaction will proceed spontaneously.
E)making the reaction more exothermic.

Question 56

Consider the reaction NOBr(g) NO(g)+ ½Br₂(g)
A plot of [NOBr]^1 vs t gives a straight line with a slope of 2.00 M^1s^1.The order of the reaction and the rate constant,respectively,are

A)second-order and 0.500 M^1s^1.
B)first-order and 2.00 s^1.
C)second-order and 2.00 M^1s^1.
D)first-order and 0.241 s^1.
E)second-order and 16.6 M^1s^1.

Question 57

For the reaction cyclobutane(g) 2ethylene(g)at 800 K,the half-life is 0.43 s.Calculate the time needed for the concentration of cyclobutane to fall to 1/64 of its initial value.

A)2.2 s
B)2.6 s
C)16 ms
D)0.38 s
E)0.43 s

Question 58

The reaction 2NO₂(g) 2NO(g)+ O₂(g)
Is postulated to occur via the mechanism
NO₂(g)+ NO₂(g) NO(g)+ NO₃(g)
Slow
NO₃(g) NO(g)+ O₂(g)
Fast
An intermediate in this reaction is

A)NO₂(g).
B)ON-NO₃(g).
C)O₂(g).
D)NO(g).
E)NO₃(g).

Question 59

An elementary process has an activation energy of 92 kJ/mol.If the enthalpy change for the reaction is 62 kJ/mol,what is the activation energy for the reverse reaction?

A)154 kJ/mol
B)62 kJ/mol
C)92 kJ/mol
D)30 kJ/mol

Question 60

The rate law for the following mechanism is NO₂(g)+ F₂(g) NO₂F(g)+ F(g)
K₁,slow
F(g)+ NO₂(g) NO₂F(g)
K₂,fast

A)rate = k₂[NO₂]².
B)rate = k₂[NO₂][F].
C)rate = k₁[NO₂][F₂].
D)rate = k₁k₂[NO₂]².
E)rate = k₁[NO₂F][F].

Question 61

Consider the following mechanism for the production of phosgene.
Cl₂  Cl + Cl
Cl + CO  COCl
COCl + Cl  COCl₂
The molecularity of the first and second elementary reactions is ____ and ____.

Question 62

For the elementary reaction A + 2B  products,rate = k[A][B].True or false?

Question 63

The fraction of molecules that collide with a kinetic energy equal to the activation energy for a reaction decreases rapidly with an increase in temperature.True or false?

Question 64

A possible mechanism for the reaction A + B + D  E + F is
A + B C
k₁,k_-1,fast
C + D  E + F
k₂
where C is a reactive intermediate present in very low concentrations.Calculate the steady state concentration of C in terms of the rate constants for the individual steps and the concentrations of the reactants.

Question 65

In the Michaelis-Menten mechanism of enzyme reaction,the Michaelis constant,K_M,is

A)K_M = k₁/k₂.
B)K_M = k₁'/k₂.
C)K_M = (k₁' + k₂)/k₁.
D)K_M = k₁' + k₂.
E)K_M = k₁/k₁'.

Question 66

The HBr synthesis is thought to involve the following reactions:
1.Br₂  2Br
2.Br + H₂  HBr + H
3.H + Br₂  HBr + Br
4.2Br  Br₂
5.2H  H₂
"6.H + Br  HBr
The chain propagation reactions in this mechanism are reactions"

A)6.
B)1, 2, 3, and 6.
C)2 and 3.
D)1, 2, and 3.
E)2, 3, and 6.

Question 67

The reduction of M³⁺ by Cr²⁺ was studied with [Cr²⁺] 100 times the concentration of Cr²⁺.When [Cr²⁺] = 0.0050 M,the rate was 2.5 s^1.The rate constant for this reaction is

A)1.3 M^1·s^1
B)0.013 M^1·s^1
C)5.0 M^1·s^1
D)500 M^1·s^1

Question 68

Given: A + B  P rate = k[A][B] Which of the following is true?

A)k = ln 2/t_1/2
B)ln [A]_t = kt + ln [A]_o
C)[A]_t = [A]_o/(1 + kt[A]_o)
D)1/[A]_t = 1/kt

Question 69

The reaction between nitrogen dioxide and carbon monoxide is thought to occur by the mechanism 2NO₂(g) NO₃(g)+ NO(g)
K₁,slow
NO₃(g)+ CO(g) NO₂(g)+ CO₂(g)
K₂,fast
The rate law for this mechanism is

A)rate = k₁k₂[NO₂]²[CO].
B)rate = (k₁/k₂)[NO₂]²[CO].
C)rate = k₁[NO₃][NO].
D)rate = k₂[NO₃][CO].
E)rate = k₁[NO₂]².

Question 70

A possible mechanism for the reaction 2NO(g)+ O₂(g) 2NO₂(g)is: 2NO(g) N₂O₂(g)
K₁,k₁',fast
N₂O₂(g)+ O₂(g) 2NO₂(g)
K₂,slow
Application of the steady-state approximation gives

A)[N₂O₂] = 0.
B)k₁[NO]²  k₂[N₂O₂][O₂] = 0.
C)[N₂O₂] = (k₁/k₂)[NO]².
D)k₁[NO]²  k₁'[N₂O₂]  k₂[N₂O₂][O₂] = 0.
E)[N₂O₂] = (k₁/k₁')[NO]².

Question 71

The reaction 2A + B  D + E has the rate law,rate = a[A]²[B]/(b + c[A])where a,b,and c are constants.The following mechanism has been proposed for this reaction.
A + B I
k₁,k_-1
I + A  D + E
k₂
I is an unstable intermediate present in minute concentrations.Show that this mechanism leads to the observed rate law and evaluate the constants a,b,and c in terms of the rate constants k₁,k_-1,and k₂.

Question 72

The reaction profile for the mechanism NO₂(g)+ F₂(g) NO₂F(g)+ F(g)slow
F(g)+ NO₂(g) NO₂F(g)fast
Shows

A)two maxima, the first maximum being the higher.
B)two maxima, the second maximum being the higher.
C)one maximum for the second step.
D)two maxima, both the same height.

Question 73

The rate law for the following mechanism is Cl₂(g) 2Cl(g)
K₁,fast
Cl(g)+ CO(g) COCl(g)
K₂,fast
COCl(g)+ Cl₂(g) COCl₂(g)+ Cl(g)
K₃,slow

A)rate = k₃K₁0.5K₂[CO][Cl₂]^1.5.
B)rate = k₃K₁0.5K₂[CO][Cl₂]^0.5.
C)rate = k₃K₁K₂[CO][Cl₂].
D)rate = k₃[COCl][Cl₂].
E)rate = k₃[COCl][Cl₂]^1.5.

Question 74

For the reaction A  products,the following data were collected. The half-life for this reaction is

A)0.521 s
B)0.752 s
C)0.922 s
D)1.08 s

Question 75

For a zero-order reaction,the rate constant has the same units as the rate of reaction.True or false?

Question 76

Consider the reaction
A + B  C + D rate = k[A]²
The time it takes for [A] to decrease from 1.0 to 0.50 M is the same as the time it takes for [A] to decrease from0.50 to 0.25 M.True or false?

Question 77

The rate law for a reaction can be determined from the coefficients in the overall reaction.True or false?

Question 78

The reaction 2NO(g)+ O₂(g) 2NO₂(g)has H_r = 114 kJmol^1.A possible mechanism for this reaction is 2NO(g) N₂O₂(g)
Rapid equilibrium,K
N₂O₂(g)+ O₂(g) 2NO₂(g)
Slow,k
If the activation energy for the reverse reaction is 225 kJmol^1,what is the activation energy for the forward reaction?

A)Because an intermediate is involved, the forward activation energy cannot be calculated with the given information.
B)111 kJmol^1
C)339 kJmol^1
D)114 kJmol^1
E)55.5 kJmol^1

Question 79

The HBr synthesis is thought to involve the following reactions:
1.Br₂  2Br
2.Br + H₂  HBr + H
3.H + Br₂  HBr + Br
4.2Br  Br₂
5.2H  H₂
"6.H + Br  HBr
The chain termination reactions in this mechanism are reactions"

A)3, 4, and 5.
B)4 and 5.
C)4, 5, and 6.
D)6.
E)3 and 4.

Question 80

Consider the following mechanism for the destruction of ozone.
O₃ + NO  NO₂ + O₂
NO₂ + O  NO + O₂
What is the catalyst in this reaction?