Chapter 14 Chemical Kinetics Flashcards

The rate of disappearance of HBr in the gas phase reaction

2HBr (g) → H2 (g) + Br2 (g)

is 0.190 M s-1 at 150 °C. The rate of appearance of Br2 is ________ M s-1.

Answers:

2.63

0.095

0.0361

0.380

0.436

The reaction

2NOBr (g) → 2 NO (g) + Br2 (g)

is a second-order reaction with a rate constant of 0.80 M-1s-1 at 11 °C. If the initial concentration of NOBr is 0.0440 M, the concentration of NOBr after 6.0 seconds is ________.

Answers:

0.0276 M

0.0324 M

0.0363 M

0.0348 M

0.0402 M

In general, as activation energy increases, reaction rate ________.

Answers:

goes down if the reaction is exothermic

goes down if the reaction is endothermic

stays the same regardless of whether the reaction is exothermic or endothermic

goes down regardless of whether the reaction is exothermic or endothermic

none of the above

A first-order reaction has a rate constant of 0.33 min-1. It takes ________ min for the reactant concentration to decrease from 0.13 M to 0.066 M.

Answers:

0.085

0.13

0.89

2.4

2.1

A reaction was found to be second order in carbon monoxide concentration. The rate of the reaction ________ if the [CO] is doubled, with everything else kept the same.

Answers:

doubles

remains unchanged

triples

increases by a factor of 4

is reduced by a factor of 2

If the rate law for the reaction

2A + 3B → products

is first order in A and second order in B, then the rate law is rate = ________.

Answers:

k[A][B]

k[A]²[B]³

k[A][B]²

k[A]²[B]

k[A]²[B]²

The kinetics of the reaction below were studied and it was determined that the reaction rate did not change when the concentration of B was tripled. The reaction is ________ order in B.

A + B → P

Answers:

zero

first

second

third

one-half

At elevated temperatures, methylisonitrile (CH3NC) isomerizes to acetonitrile (CH3CN):

CH3NC (g) → CH3CN (g)

The reaction is first order in methylisonitrile. The attached graph shows data for the reaction obtained at 198.9 °C.

The rate constant for the reaction is ________ s-1.

Answers:

-1.9 × 104

+1.9 × 104

-5.2 × 10-5

+5.2 × 10-5

+6.2

One difference between first- and second-order reactions is that ________.

Answers:

the half-life of a first-order reaction does not depend on [A]0; the half-life of a second-order reaction does depend on [A]0

the rate of both first-order and second-order reactions do not depend on reactant concentrations

the rate of a first-order reaction depends on reactant concentrations; the rate of a second-order reaction does not depend on reactant concentrations

a first-order reaction can be catalyzed; a second-order reaction cannot be catalyzed

None of the above are true.

The decomposition of N2O5 in solution in carbon tetrachloride proceeds via the reaction

2N2O5 (soln) → 4NO2 (soln) + O2 (soln)

The reaction is first order and has a rate constant of 4.82 × 10-3 s-1 at 64 °C. If the reaction is initiated with 0.072 mol in a 1.00-L vessel, how many moles remain after 151 s?

Answers:

0.067

0.074

0.035

9.6

1.6 × 103

The rate of a reaction depends on ________.

Answers:

collision frequency

collision energy

collision orientation

all of the above

none of the above

The half-life of a first-order reaction is 13 min. If the initial concentration of reactant is 0.085 M, it takes ________ min for it to decrease to 0.055 M.

Answers:

8.2

113.6

0.048

8.4

The rate constant for a second-order reaction is 0.13 M-1s-1. If the initial concentration of reactant is 0.26 mol/L, it takes ________ s for the concentration to decrease to 0.07 mol/L.

Answers:

0.017

1.4

14

80

10

The overall order of a reaction is 2. The units of the rate constant for the reaction are ________.

Answers:

M/s

M-1s-1

1/s

1/M

s/M2

The combustion of ethylene proceeds by the reaction

C2H4 (g) + 3O2 (g) → 2CO2 (g) + 2H2O (g)

When the rate of disappearance of O2 is 0.13 M s-1, the rate of appearance of CO2 is ________ M s-1.

Answers:

0.087

0.043

0.39

0.20

0.26

At elevated temperatures, methylisonitrile (CH3NC) isomerizes to acetonitrile (CH3CN):

CH3NC (g) → CH3CN (g)

At the start of the experiment, there are 0.200 mol of reactant (CH3NC) and 0 mol of product (CH3CN) in the reaction vessel. After 25 min of reaction, 0.108 mol of reactant (CH3NC) remain. The average rate of decomposition of methyl isonitrile, CH3NC, in this 25 min period is ________ mol/min.

Answers:

3.7 × 10-3

0.092

2.3

4.3 × 10-3

0.54

The kinetics of the reaction below were studied and it was determined that the reaction rate did not change when the concentration of B was tripled. The reaction is ________ order in B.

A + B → P

Answers:

zero

first

second

third

one-half

The reaction A (aq) → B (aq) is first order in [A]. A solution is prepared with [A] = 1.22 M. The following data are obtained as the reaction proceeds:

Time(s) / 0.0 / 6.0 / 12.0 / 18.0 /

[A] (M) / 1.22 / 0.61 / 0.31 / 0.15 /

The rate constant for this reaction is ________ s-1.

Answers:

0.23

1.0

0.17

0.12

-0.12

At elevated temperatures, dinitrogen pentoxide decomposes to nitrogen dioxide and oxygen:

2N2O5(g) → 4NO2 (g) + O2 (g)

When the rate of formation of NO2 is 5.5 × 10-4 M/s, the rate of decomposition of N2O5 is ________ M/s.

Answers:

2.2 × 10-3

1.4 × 10-4

10.1 × 10-4

2.8 × 10-4

5.5 × 10-4

The reaction below is first order in [H2O2]:

2H2O2 (l) → 2H2O (l) + O2 (g)

A solution originally at 0.600 M H2O2 is found to be 0.075 M after 54 min. The half-life for this reaction is ________ min.

Answers:

6.8

18

14

28

54

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g) →B(g). The following data are obtained for [A] as the reaction proceeds:

Time (s) / 0.00 / 10.0 / 20.0 / 30.0 / 40.0 /

Moles of [A] / 0.124 / 0.110 / 0.088 / 0.073 / 0.054 /

How many moles of B are present at 30 s?

Answers:

2.4 × 10-3

0.15

0.073

1.7 × 10-3

0.051

If the rate law for the reaction

2A + 3B → products

is second order in A and first order in B, then the rate law is rate = ________.

Answers:

k[A][B]

k[A]²[B]³

k[A][B]²

k[A]²[B]

k[A]²[B]²

The mechanism for formation of the product X is:

A + B → C + D (slow)

B + D → X (fast)

The intermediate reactant in the reaction is ________.

Answers:

A

B

C

D

X

What is the order of the reaction with respect to ClO2?

2 ClO2 (aq) + 2 OH- (aq) → ClO3- (aq) + ClO2- (aq) + H2O (1)

Experiment # / [CLO2] (M) / [OH-] (M) / Initial Rate(M/s) /

#1 / 0.060 / 0.030 / 0.0248 /

#2 / 0.020 / 0.030 / 0.00276 /

#3 / 0.020 / 0.090 / 0.00828 /

Answers:

0

1

2

3

4

Nitrogen dioxide decomposes to nitric oxide and oxygen via the reaction:

2NO2 (g) → 2NO (g) + O2 (g)

In a particular experiment at 300 °C, [NO2] drops from 0.0100 to 0.00800 M in 100 s. The rate of appearance of O2 for this period is ________ M/s.

Answers:

1.0 × 10-5

2.0 × 10-5

4.0 × 10-5

2.0 × 10-3

4.0 × 10-3

In general, as temperature goes up, reaction rate ________.

Answers:

goes up if the reaction is exothermic

goes up if the reaction is endothermic goes up regardless of whether the reaction is exothermic or endothermic

stays the same regardless of whether the reaction is exothermic or endothermic

stays the same if the reaction is first order

A second-order reaction has a half-life of 18 s when the initial concentration of reactant is 0.71 M. The rate constant for this reaction is ________ M-1s-1.

Answers:

7.8 × 10-2

3.8 × 10-2

2.0 × 10-2

1.3

18

Nitrogen dioxide decomposes to nitric oxide and oxygen via the reaction:

2NO2 (g) → 2NO (g) + O2 (g)

In a particular experiment at 300 °C, [NO2] drops from 0.0100 to 0.00800 M in 100 s. The rate of appearance of O2 for this period is ________ M/s.

Answers:

1.0 × 10-5

2.0 × 10-5

4.0 × 10-5

2.0 × 10-3

4.0 × 10-3

The mechanism for formation of the product X is:

A + B → C + D (slow)

B + D → X (fast)

The intermediate reactant in the reaction is ________.

Answers:

A

B

C

D

X

The concentration of A is ________ M after 40.0 s.

The reaction A → B is first order in [A]. Consider the following data.

Time (s) / 0.00 / 5.0 / 10.0 / 15.0 / 20.0 /

Moles of [A] / 0.20 / 0.14 / 0.10 / 0.071 / 0.050 /

Answers:

1.3 × 10-2

3.0 × 10-2

14

0.46

4.0 × 102

The reaction A (aq) → B (aq) is first order in [A]. A solution is prepared with [A] = 1.22 M. The following data are obtained as the reaction proceeds:

Time (s) / 0.0 / 6.0 / 12.0 / 18.0 /

[A] [M] / 1.22 / 0.61 / 0.31 / 0.15 /

The rate constant for this reaction is ________ s-1.

Answers:

0.23

1.0

0.17

0.12

-0.12

A catalyst can increase the rate of a reaction ________.

Answers:

by changing the value of the frequency factor (A)

by increasing the overall activation energy (Ea) of the reaction

by lowering the activation energy of the reverse reaction by providing an alternative pathway with a lower activation energy

All of these are ways that a catalyst might act to increase the rate of reaction.

The rate of a reaction depends on ________.

Answers:

collision frequency

collision energy

collision orientation

all of the above

none of the above

The half-life of a first-order reaction is 13 min. If the initial concentration of reactant is 0.085 M, it takes ________ min for it to decrease to 0.055 M.

Answers:

8.2

113.6

0.048

8.4

Of the following, all are valid units for a reaction rate except ________.

Answers:

mol/L

M/s

mol/hr

g/s

mol/L-hr

A particular first-order reaction has a rate constant of 1.35 × 102 s-1 at 25.0 °C. What is the magnitude of k at 65.0 °C if Ea = 55.5 kJ/mol?

Answers:

1.92 × 103

1.95 × 104

358

3.48 × 1073

1.35 × 102

The rate of a reaction depends on ________.

Answers:

collision frequency

collision energy

collision orientation

all of the above

none of the above

In the Arrhenius equation,

k = Ae-Ea/RT

________ is the frequency factor.

Answers:

k

A

e

Ea

R

Of the units below, ________ are appropriate for a third-order reaction rate constant.

Answers:

M-2s-1

M s-1

s-1

M-1s-1

mol/L

The rate law of a reaction is rate = k[D][X]. The units of the rate constant are ________.

Answers:

mol L-1s-1

L mol-1s-1

mol2 L-2s-1

mol L-1s-2

L2 mol-2s-1

The combustion of ethylene proceeds by the reaction

C2H4 (g) + 3O2 (g) → 2CO2 (g) + 2H2O (g)

When the rate of disappearance of O2 is 0.13 M s-1, the rate of appearance of CO2 is ________ M s-1.

Answers:

0.087

0.043

0.39

0.20

0.26

The kinetics of the reaction below were studied and it was determined that the reaction rate did not change when the concentration of B was tripled. The reaction is ________ order in B.

A + B → P

Answers:

zero

first

second

third

one-half

Which substance in the reaction below either appears or disappears the fastest?

4NH3 + 7O2 → 4NO2 + 6H2O

Answers:

NH3

O2

NO2

H2O

The rates of appearance/disappearance are the same for all of these.

The magnitude of the rate constant is ________.

A + B → P

Experiment # / [A] (M) / [B] (M) / Initial Rate(M/s) /

#1 / 0.273 / 0.763 / 2.83 /

#2 / 0.273 / 1.526 / 2.83 /

#3 / 0.819 / 0.763 / 25.47 /

Answers:

38.0

0.278

13.2

42.0

2.21

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g) →B(g).

The following data are obtained for [A] as the reaction proceeds:

Time (s) / 0.00 / 10.0 / 20.0 / 30.0 / 40.0 /

Moles of [A] / 0.124 / 0.110 / 0.088 / 0.073 / 0.054 /

How many moles of B are present at 10 s?

Answers:

0.011

0.220

0.110

0.014

1.4 × 10-3

If the rate law for the reaction

2A + 3B → products

is second order in A and first order in B, then the rate law is rate = ________.

Answers:

k[A][B]

k[A]²[B]³

k[A][B]²

k[A]²[B]

k[A]²[B]²

Of the following, all are valid units for a reaction rate except ________.

Answers:

mol/L

M/s

mol/hr

g/s

mol/L-hr

The reaction A (aq) → B (aq) is first order in [A]. A solution is prepared with [A] = 1.22 M. The following data are obtained as the reaction proceeds:

Time (s) / 0.0 / 6.0 / 12.0 / 18.0 /

[A] [M] / 1.22 / 0.61 / 0.31 / 0.15 /

The rate constant for this reaction is ________ s-1.

Answers:

0.23

1.0

0.17

0.12

-0.12

Consider the following reaction:

A → 2C

The average rate of appearance of C is given by Δ[C]/Δt. Comparing the rate of appearance of C and the rate of disappearance of A,

we get Δ[C]/Δt = ________ × (-Δ[A]/Δt).

Answers:

+2

-1

+1

+1/2

-1/2

The rate law for a reaction is

rate = k[A][B]

Which one of the following statements is false?

Answers:

The reaction is first order overall.

The reaction is first order in A.

The reaction is first order in [B].

k is the reaction rate constant

If [A] is doubled, the reaction rate will increase by a factor of 2.

The reaction

CH3-N≡C → CH3-C≡N

is a first-order reaction. At 230.3 °C, k = 6.29 × 10-4s-1. If CH3-N≡C is 1.00 × 10-3 initially, CH3-N≡C is ________ after 1.000 × 103 s.

Answers:

5.33 × 10-4

2.34 × 10-4

1.88 × 10-3

4.27 × 10-3

1.00 × 10-6

The reaction below is first order in [H2O2]:

2H2O2 (l) → 2H2O (l) + O2 (g)

A solution originally at 0.600 M H2O2 is found to be 0.075 M after 54 min. The half-life for this reaction is ________ min.

Answers:

6.8

18

14

28

54

The overall order of a reaction is 1. The units of the rate constant for the reaction are ________.

Answers:

M/s

M-1s-1

1/s

1/M

s/M2

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g) →B(g). The following data are obtained for [A] as the reaction proceeds:

Time (s) / 0.00 / 10.0 / 20.0 / 30.0 / 40.0 /

Moles of [A] / 0.124 / 0.110 / 0.088 / 0.073 / 0.054 /

The average rate of appearance of B between 20 s and 30 s is ________ mol/s.

Answers:

+1.5 × 10-3

+5.0 × 10-4

-1.5 × 10-3

+7.3 × 10-3

-7.3 × 10-3

The reaction A (aq) → B (aq) is first order in [A]. A solution is prepared with [A] = 1.22 M. The following data are obtained as the reaction proceeds:

Time: 0.0 / 0.6 / 0.22 /. 0.18

[A](M): 1.22 / 0.61 / 0.31 / 0.15

The rate constant for this reaction is ________ s-1.

Answers:

0.23

1.0

0.17

0.12

-0.12

he combustion of ethylene proceeds by the reaction

C2H4 (g) + 3O2 (g) → 2CO2 (g) + 2H2O (g)

When the rate of disappearance of O2 is 0.13 M s-1, the rate of disappearance of C2H4 is ________ M s-1.

Answers:

0.087

0.043

0.39

0.20

0.26

At elevated temperatures, methylisonitrile (CH3NC) isomerizes to acetonitrile (CH3CN):

CH3NC (g) → CH3CN (g)

The dependence of the rate constant on temperature is studied and the graph below is prepared from the results.

The energy of activation of this reaction is ________ kJ/mol.

Answers:

160

1.6 × 105

4.4 × 10-7

4.4 × 10-4

1.9 × 104

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g) →B(g). The following data are obtained for [A] as the reaction proceeds:

Time (s) / 0.00 / 10.0 / 20.0 / 30.0 / 40.0 /

Moles of [A] / 0.124 / 0.110 / 0.088 / 0.073 / 0.054 /

the average rate of disappearance of A between 20 s and 40 s is ________ mol/s.

Answers:

8.5 × 10-4

1.7 × 10-3

590

7.1 × 10-3

1.4 × 10-3

In general, as activation energy increases, reaction rate ________.

Answers:

goes down if the reaction is exothermic goes down if the reaction is endothermic

stays the same regardless of whether the reaction is exothermic or endothermic

goes down regardless of whether the reaction is exothermic or endothermic

none of the above

t elevated temperatures, methylisonitrile (CH3NC) isomerizes to acetonitrile (CH3CN):

CH3NC (g) → CH3CN (g)

At the start of the experiment, there are 0.200 mol of reactant (CH3NC) and 0 mol of product (CH3CN) in the reaction vessel. After 25 min of reaction, 0.108 mol of reactant (CH3NC) remain. The average rate of decomposition of methyl isonitrile, CH3NC, in this 25 min period is ________ mol/min.

Answers:

3.7 × 10-3

0.092

2.3

4.3 × 10-3

0.54

A second-order reaction has a half-life of 12 s when the initial concentration of reactant is 0.98 M. The rate constant for this reaction is ________ M-1s-1.

Answers:

12

2.0 × 10-2

8.5 × 10-2

4.3 × 10-2

4.3

Nitrogen dioxide decomposes to nitric oxide and oxygen via the reaction:

2NO2 (g) → 2NO (g) + O2 (g)

In a particular experiment at 300 °C, [NO2] drops from 0.0100 to 0.00800 M in 100 s. The rate of appearance of O2 for this period is ________ M/s.

Answers:

1.0 × 10-5

2.0 × 10-5

4.0 × 10-5

2.0 × 10-3

4.0 × 10-3

For the elementary reaction

NO3 + CO → NO2 + CO2

the molecularity of the reaction is ________, and the rate law is equal to:

Answers:

2, k[NO3][CO]

4, k[NO3][CO][NO2][CO2]

2, k[NO2][CO2]

2, k[NO3][CO]/[NO2][CO2]

4, k[NO2][CO2]/[NO3][CO]