Practice Ch 15

Ch 15 Practice Problems

Use the following to answer question 1:For the reaction 2A + B productsthe following mechanism is proposed: A + B M A + M products

1. T F True or False? A catalyst never appears in a rate law.

2. The average rate of disappearance of ozone in the reaction 2O3(g) 3O2(g) is found to be 8.9 10–3 atm over a certain interval of time. What is the rate of appearance of O2 during this interval?A) 1.3 10–2 atm/timeB) 8.9 10–3 atm/timeC) 5.9 10–3 atm/timeD) 2.7 10–2 atm/timeE) 1.8 10–2 atm/time

Use the following to answer question 3:

For the reaction 2N2O5(g) 4NO2(g) + O2(g), the following data were collected.t (minutes) [N2O5] (mol/L)

0 1.24 10–2

10. 0.92 10–2

20. 0.68 10–2

30. 0.50 10–2

40. 0.37 10–2

50. 0.28 10–2

70. 0.15 10–2

3. The initial rate of production of NO2 for this reaction is approximatelyA) 6.4 10–4 mol/L • minB) 3.2 10–4 mol/L • minC) 1.24 10–2 mol/L • minD) 1.6 10–4 mol/L • minE) none of these

4. The rate constant k is dependent onA) the concentration of the reactant.B) the concentration of the product.C) the temperature.D) the order of the reaction.E) none of these

Use the following to answer questions 5-7:

The oxidation of Cr3+ to CrO42– can be accomplished using Ce4+ in a buffered solution. The following data were obtained:

RelativeInitial Rate [Ce4+]0 [Ce3+]0 [Cr3+]0

1 2.0 10–3 1.0 10–2 3.0 10–2

2 4.0 10–3 2.0 10–2 3.0 10–2

4 4.0 10–3 1.0 10–2 3.0 10–2

16 8.0 10–3 2.0 10–2 6.0 10–2

5. Determine the order in the rate law of the species Ce4+.A) 1B) 2C) 3D) –1E) –2

6. Determine the order in the rate law of the species Ce3+.A) 1B) 2C) 3D) –1E) –2

7. Determine the order in the rate law of the species Cr3+.A) 1B) 2C) 3D) –1E) –2

8. The balanced equation for the reaction of bromate ion with bromide in acidic solution is BrO+ 5Br– + 6H+ 3Br2 + 3H2O

At a particular instant in time, the value of –[Br–]/t is 2.0 10–3 mol/L • s. What is the value of [Br2]/t in the same units?

A) 1.2 10–3

B) 6.0 10–3

C) 3.3 10–3

D) 3.3 10–5

E) 2.0 10–3


The following questions refer to the hypothetical reaction A + B products. The kinetics data given can be analyzed to answer the questions.

[A]0 [B]0 Rate of decrease(mol/L) (mol/L) of [A] (M/s)

5.0 5.0 X10.0 5.0 2X 5.0 10.0 2X

Time (s) [B] (mol/L)10.0 10020.0 10030.0 100

9. The rate law for the reaction is Rate = k[A]x[B]y. What are the values of x and y?A) x = 0 y = 1B) x = 1 y = 0C) x = 1 y = 1D) x = 2 y = 1E) x = 1 y = 2

10. What form will the pseudo-rate law have?A) Rate = k'[A]xB) Rate = k'[B]yC) Rate = k'[A]x[B]yD) Rate = kk'[A]xE) Rate = kk'[B]y

11. The rate expression for a particular reaction is Rate = k[A][B]2. If the initial concentration of B is increased from 0.1 M to 0.3 M, the initial rate will increase by which of the following factors?A) 3B) 27C) 4D) 6E) 9


A general reaction written as 2A + 2B C + 2D is studied and yields the following data.[A]0 [B]0 Initial [C]/t

0.100 M 0.100 M 4.00 10–5 mol/L • s0.200 M 0.100 M 4.00 10–5 mol/L • s

0.100 M 0.200 M 8.00 10–5 mol/L • s

12. For the first of the reactions in the table of data, determine -[B]/t.A) 4.00 10–5

B) 8.00 10–5

C) 1.60 10–4

D) 2.00 10–5

E) none of these

13. What is the order of the reaction with respect to B?A) 1B) 4C) 3D) 2E) 0

14. What is the order of the reaction with respect to A?A) 1B) 4C) 3D) 2E) 0

15. What is the overall order of the reaction?A) 1B) 4C) 3D) 2E) 0

16. What are the proper units for the rate constant for the reaction?A) s–1

B) mol L–1 s–1

C) L mol–1 s–1

D) L3 mol–3 s–1

E) L2 mol–2 s–1

17. What is the numerical value of the rate constant?A) 4.00 10–4

B) 4.00 10–3

C) 4.00 10–2

D) 4.00 10–1

E) none of these

18. The following data were obtained for the reaction of NO with O2. Concentrations are in molecules/cm3 and rates are in molecules/cm3 • s.

[NO]0 [O2]0 Initial Rate1 1018 1 1018 2.0 1016

2 1018 1 1018 8.0 1016

3 1018 1 1018 18.0 1016

1 1018 2 1018 4.0 1016

1 1018 3 1018 6.0 1016

Which of the following is the correct rate law?

A) Rate = k[NO][O2]B) Rate = k[NO][O2]2

C) Rate = k[NO]2[O2]D) Rate = k[NO]2

E) Rate = k[NO]2[O2]2

19. A first-order reaction is 43% complete at the end of 18 min. What is the value of the rate constant?A) 3.1 x 10-2 min-1

B) 0.21 min-1

C) 0.031 min-1

D) 4.7 10-2 min-1

E) 1.4 10-2 min-1


The reactionH2SeO3(aq) + 6I–(aq) + 4H+(aq) 2I3

–(aq) + 3H2O(l) + Se(s)was studied at 0°C by the method of initial rates:

[H2SeO3]0 [H+]0 [I–]0 Rate (mol/L • s)1.0 10–4 2.0 10–2 2.0 10–2 1.66 10–7

2.0 10–4 2.0 10–2 2.0 10–2 3.33 10–7

3.0 10–4 2.0 10–2 2.0 10–2 4.99 10–7

1.0 10–4 4.0 10–2 2.0 10–2 6.66 10–7

1.0 10–4 1.0 10–2 2.0 10–2 0.42 10–7

1.0 10–4 2.0 10–2 4.0 10–2 13.4 10–7

1.0 10–4 1.0 10–2 4.0 10–2 3.36 10–7

20. What is the rate law?A) Rate = k[H2SeO3][H+][I–]B) Rate = k[H2SeO3][H+]2[I–]C) Rate = k[H2SeO3][H+][I–]2

D) Rate = k[H2SeO3]2[H+][I–]E) Rate = k[H2SeO3][H+]2[I–]3

21. What is the numerical value of the rate constant?A) 5.2 105

B) 2.1 102

C) 4.2D) 1.9 10–6

E) none of these

22. Use the following initial rate data for the reaction in aqueous solution to determine the rate law.

[CH3COCH3]0 (M) [Br2]0 (M) [H+]0 (M) (M/s)1.00 1.00 1.00 4.0 10–3

2.00 1.00 1.00 8.0 10–3

2.00 2.00 1.00 8.0 10–3

1.00 2.00 2.00 8.0 10–3

A) Rate = k[Br2][H+]B) Rate = k[CH3COCH3][Br2]C) Rate = k[CH3COCH3][H+]D) Rate = k[CH3COCH3][Br2][H+]E) Rate = k[CH3COCH3][Br2][H+]2

23. Initial rate data have been determined at a certain temperature for the gaseous reaction 2NO + 2H2 N2 + 2H2O

[NO]0 (M) [H2]0 (M) Initial Rate (M/s)0.16 0.32 0.02000.16 0.48 0.03000.32 0.32 0.0800

What is the numerical value of the rate constant?

A) 2.4B) 7.6C) 0.39D) 1.2E) 0.13

24. What is the rate law for the following reaction, given the data below? 2NO + H2 N2O + H2O

Experiment Initial [NO](mol/L)

Initial [H2](mol/L)

Initial Rate of Disappearance of NO

(mol/L • s)1 6.4 10–3 2.2 10–3 2.6 10–5

2 12.8 10–3 2.2 10–3 1.0 10–4

3 6.4 10–3 4.5 10–3 5.1 10–5

A) Rate = k[NO]B) Rate = k[NO]2

C) Rate = k[NO]2[H2]D) Rate = k[NO][H2]E) Rate = k[N2O][H2O]


The following questions refer to the hypothetical reaction A + B products. The kinetics data given can be analyzed to answer the questions.

[A]0 [B]0 Rate of decrease(mol/L) (mol/L) of [A] (M/s)

5.0 5.0 X10.0 5.0 2X 5.0 10.0 2X

Time (s) [B] (mol/L)10.0 10020.0 10030.0 100

25. Determine the magnitude of the pseudo-rate constant (k') if the magnitude of X in the rate data is 0.00905.A) 4.3 10–3

B) 1.2 10–2

C) 0.86D) 0.31E) 1.81 10–3

26. For the reaction A + B products, the following data were obtained.Initial Rate (mol/L • s) 0.030 0.059 0.060 0.090 0.090[A]0 (mol/L) 0.10 0.20 0.20 0.30 0.30[B]0 (mol/L) 0.20 0.20 0.30 0.30 0.50What is the experimental rate law?

A) Rate = k[A]B) Rate = k[B]C) Rate = k[A][B]D) Rate = k[A]2[B]E) Rate = k[A][B] 2

27. The reaction of (CH3)3CBr with hydroxide ion proceeds with the formation of (CH3)3COH. (CH3)3CBr (aq) + OH– (aq) (CH3)3COH (aq) + Br– (aq)

The following data were obtained at 55°C.

[(CH3)3CBr]0 [HO–]0 Initial Rate Exp. (mol/L) (mol/L) (mol/L • s)

1 0.10 0.10 1.0 10–3

2 0.20 0.10 2.0 10–3

3 0.10 0.20 1.0 10–3

4 0.30 0.20 ?

What will the initial rate (in mol/L • s) be in Experiment 4?

A) 3.0 10–3

B) 6.0 10–3

C) 9.0 10–3

D) 18 10–3

E) none of these

28. For the reaction in which A and B react to form C, the following initial rate data were obtained.[A]0

(mol/L)[B]0

(mol/L)Initial Rate of Formation of C

(mol/L • s)0.300 0.300 2.800.300 0.150 0.7000.600 0.150 1.40

What is the rate law for the reaction?

A) Rate = k[A][B]B) Rate = k[A]2[B]C) Rate = k[A][B]2

D) Rate = k[A]2[B]2

E) Rate = k[A]3

29. Tabulated below are initial rate data for the reaction 2Fe(CN)6

3– + 2I– 2Fe(CN)64– + I2

Run [Fe(CN)63–]0

(M)[I–]0

(M)[Fe(CN)6

4–]0

(M)[I2]0

(M)Initial Rate

(M/s)1 0.01 0.01 0.01 0.01 1 10–5

2 0.01 0.02 0.01 0.01 2 10–5

3 0.02 0.02 0.01 0.01 8 10–5

4 0.02 0.02 0.02 0.01 8 10–5

5 0.02 0.02 0.02 0.02 8 10–5

What is the experimental rate law?

A) = k[Fe(CN)63–]2[I–]2[Fe(CN)6

4–]2[I2]

B) = k[Fe(CN)63–]2[I–][Fe(CN)6

4–][I2]

C) = k[Fe(CN)63–]2[I–]

D) = k[Fe(CN)63–][I–]2

E) = k[Fe(CN)63–][I–] [Fe(CN)6

4–]

30. Tabulated below are initial rate data for the reaction 2Fe(CN)6

3– + 2I– 2Fe(CN)64– + I2

Run [Fe(CN)63–]0

(M)[I–]0

(M)[Fe(CN)6

4–]0

(M)[I2]0

(M)Initial Rate

(M/s)1 0.01 0.01 0.01 0.01 1 10–5

2 0.01 0.02 0.01 0.01 2 10–5

3 0.02 0.02 0.01 0.01 8 10–5

4 0.02 0.02 0.02 0.01 8 10–5

5 0.02 0.02 0.02 0.02 8 10–5

What is the value of k?

A) 107 M–5 s–1

B) 103 M–3 s–1

C) 10 M–2 s–1

D) 50 M–2 s–1

E) none of these


The following initial rate data were found for the reaction 2MnO4

– + 5H2C2O4 + 6H+ 2Mn2+ + 10CO2 + 8H2O[MnO4

–]0 [H2C2O4]0 [H+]0 Initial Rate (M/s)1 10–3 1 10–3 1.0 2 10–4

2 10–3 1 10–3 1.0 8 10–4

2 10–3 2 10–3 1.0 1.6 10–3

2 10–3 2 10–3 2.0 1.6 10–3

31. Which of the following is the correct rate law?A) Rate = k[MnO4

–]2[H2C2O4]5[H+]6

B) Rate = k[MnO4–]2[H2C2O4][H+]

C) Rate = k[MnO4–][H2C2O4][H+]

D) Rate = k[MnO4–]2[H2C2O4]

E) Rate = k[MnO4–][H2C2O4]2

32. What is the value of the rate constant?A) 2 105 M • s–1

B) 2 105 M–2 • s–1

C) 200 M–1 • s–1

D) 200 M–2 • s–1

E) 2 10–4 M • s–1

33. For which order reaction is the half-life of the reaction independent of the initial concentration of the reactant(s)?A) zero orderB) first orderC) second orderD) all of theseE) none of these

34. The reaction A B + C is known to be zero order in A with a rate constant of 5.0 10–2 mol/L • s at 25° C. An experiment was run at 25°C where [A]0 = 1.0 10–3 M. What is the integrated rate law?A) [A] = ktB) [A] – [A]0 = kt

C) = kt

D) ln = ktE) [A]0 – [A] = kt


Two isomers (A and B) of a given compound dimerize as follows:

Both processes are known to be second order in reactant, and k1 is known to be 0.25 L/mol • s at 25° C, where

Rate = – = k1[A]2

In a particular experiment, A and B were placed in separate containers at 25° C, where [A] 0 = 1.0 10–2 M and [B]0 = 2.5 10–

2 M. It was found that [A] = 3[B] after the reactions progressed for 3.0 min.

35. Calculate the half-life for the reaction involving A.A) 4.0 102 sB) 1.7 101 sC) 2.5 103

D) 1.8 102 sE) none of these

36. The OH radical disproportionates according to the elementary chemical reaction OH + OH H2O + O. This reaction is second order in OH. The rate constant for the reaction is 2.4 10–12 cm3/molecule • s at room temperature. If the initial OH concentration is 1.7 1013 molecules/cm3, what is the first half-life for the reaction?A) 3.5 1024 sB) 2.9 1011 sC) 0.025 sD) 4.9 sE) 4.2 s


The decomposition of N2O5(g) to NO2(g) and O2(g) obeys first-order kinetics. Assume the form of the rate law is

Rate = – = k[N2O5] where k = 3.4 10–5 s–1 at 25°C.

37. What is the initial rate of reaction at 25°C where [N2O5]0 = 5.0 10–2 M?A) 3.4 10–5 mol/L • sB) 1.7 10–6 mol/L • sC) 6.8 10–4 mol/L • sD) 5.0 10–2 mol/L • sE) none of these

38. What is the half-life for the reaction described?A) 5.9 105 sB) 2.0 104 sC) 2.4 10–5 sD) 7.4 102 sE) none of these

39. The reaction A B + C is known to be zero order in A with a rate constant of 3.8 10–2 mol/L • s at 25° C. An experiment was run at 25°C where [A]0 = 1.8 10–3 M. What is the rate after 6.7 minutes?A) 3.8 10–2 mol/L • sB) 1.5 10–11 mol/L • sC) 6.7 10–4 mol/L • sD) 1.8 10–3 mol/L • sE) 6.8 10–5 mol/L • s

40. For which of the following is the half-life directly dependent on the concentration of the reactant?A) zero-order reactionB) first-order reactionC) second-order reactionD) two of theseE) all of these

41. If the reaction 2HI H2 + I2 is second order, which of the following will yield a linear plot?A) log [HI] vs. timeB) 1/[HI] vs. timeC) [HI] vs. timeD) ln [HI] vs. time


For the reaction a A products, select the reaction order(s) that best fit(s) the observations.

42. The half-life is constant.A) zero order in AB) first order in A C) second order in AD) all of theseE) none of these

43. A plot of [A] vs. t is a straight line.A) zero order in A B) first order in AC) second order in AD) all of theseE) none of these

44. A plot of k vs. 1/T gives a straight line.A) zero order in AB) first order in AC) second order in AD) all of theseE) none of these

45. [A] is constant.A) zero order in AB) first order in AC) second order in AD) all of theseE) none of these

46. A plot of [A]2 vs. t gives a straight line.A) zero order in AB) first order in AC) second order in A D) all of theseE) none of these

47. The rate is constant over time.A) zero order in A B) first order in AC) second order in AD) all of theseE) none of these

48. The half-life decreases over time.A) zero order in A B) first order in AC) second order in AD) all of theseE) none of these

49. The reaction A B + C is known to be zero order in A with a rate constant of 3.6 10–2 mol/L • s at 25° C. An experiment was run at 25°C where [A]0 = 3.4 10–3 M. What is the half-life for the reaction?A) 4.7 10–2 sB) 1.9 101 sC) 1.8 10–2 sD) 8.2 104 sE) 6.1 10–2 s

50. For which order reaction is the half-life of the reaction proportional to 1/k (k is the rate constant)?A) zero orderB) first orderC) second orderD) all of theseE) none of these


The following questions refer to the gas-phase decomposition of chloroethane:C2H5Cl products

Experiment shows that the decomposition is first order. The following data show kinetics information for this reaction.

Time (s) ln [C2H5Cl] (M)

1.0 -1.625

2.0 -1.735

51. What is the rate constant for this decomposition?A) 0.29/sB) 0.35/sC) 0.11/sD) 0.02/sE) 0.22/s


The reaction 2NOBr 2NO + Br2

exhibits the rate law

Rate = k[NOBr]2 = – where k = 1.0 10–5 M–1 • s–1 at 25° C. This reaction is run where the initial concentration of NOBr ([NOBr] 0) is 1.00 10–1 M.

52. What is one half-life for this experiment?A) 5.0 10–1 sB) 6.9 104 sC) 1.0 10–5 sD) 1.0 106 sE) none of these

53. The [NO] after 1.00 h has passed isA) 3.5 10–4 MB) 9.9 10–3 MC) 9.7 10–3 MD) 1.0 10–3 ME) none of these


For the reaction 2N2O5(g) 4NO2(g) + O2(g), the following data were collected.t (minutes) [N2O5] (mol/L)

0 1.24 10–2

10. 0.92 10–2

20. 0.68 10–2

30. 0.50 10–2

40. 0.37 10–2

50. 0.28 10–2

70. 0.15 10–2

54. The half-life of this reaction is approximatelyA) 15 minB) 18 minC) 23 minD) 36 minE) 45 min

55. The order of this reaction in N2O5 isA) 0B) 1C) 2D) 3E) none of these

56. The concentration of O2 at t = 10. min isA) 2.0 10–4 mol/LB) 0.32 10–2 mol/LC) 0.16 10–2 mol/LD) 0.64 10–2 mol/LE) none of these

57. The concentration N2O5 at 100 min will be approximatelyA) 0.03 10–2 mol/LB) 0.06 10–2 mol/LC) 0.10 10–2 mol/LD) 0.01 10–2 mol/LE) none of these


For a reaction aA products, [A]0 = 4.0 M, and the first three successive half-lives are 48, 96, and 192 min.

58. Calculate k (without units).A) 5.2 10-3

B) 2.6 10-3

C) 4.1 10-3

D) 1.4 10-2

E) none of these

59. Calculate [A] at t = 81 min.A) 1.3 MB) 1.5 MC) 2.6 MD) 3.0 ME) none of these

60. The reaction 2NO N2 + O2 has the following rate law:

After a period of 2.0 103 s, the concentration of NO falls from an initial value of 2.8 10–3 mol/L to 2.0 10–4 mol/L. What is the rate constant, k?

A) 7.2 10–2 M–1/sB) 1.7 10–4 M–1/sC) 4.0 10–4 M–1/sD) 4.0 10–7 M–1/sE) 3.6 10–2 M–1/s

61. The reaction A B + C is known to be zero order in A with a rate constant of 4.8 10–2 mol/L • s at 25° C. An experiment was run at 25°C where [A]0 = 2.2 M. What is the concentration of B after 6.0 s?A) 8.5 10–1 MB) 1.9 MC) 1.1 10–1 MD) 2.9 10–1 ME) 2.2 M

62. At 760 K, acetaldehyde decomposes to carbon monoxide and methane: CH3CHO CH4 + CO

A plot of ln [CH3CHO] versus time is linear. After 530 s, [CH3CHO] decreases to one half of its initial value of 0.10 M. What is the rate law for the reaction?

A)

B)

C)

D)

E)


The following questions refer to the gas-phase decomposition of chloroethane:C2H5Cl products

Experiment shows that the decomposition is first order. The following data show kinetics information for this reaction.

Time (s) ln [C2H5Cl] (M)

1.0 -1.625

2.0 -1.735

63. What was the initial concentration of the ethylene chloride?A) 0.29 MB) 0.35 MC) 0.11 MD) 0.02 ME) 0.22 M

64. What would the concentration be after 5.0 s?A) 0.13 MB) 0.08 MC) 0.02 MD) 0.19 ME) 0.12 M

65. What is the time to half-life?A) 0.7 sB) 1.3 sC) 8.9 sD) 6.3 sE) 2.2 s

66. The reaction 2N2O5(g) O2(g) + 4NO2(g)

is first order in N2O5. For this reaction at 45° C, the rate constant k = 1.0 10–5 s–1, where the rate law is defined as

Rate = – = k[N2O5]

For a particular experiment ([N2O5]0 = 1.0 10–3 M), calculate [N2O5] after 1.0 105 s.

A) 5.0 10–4 MB) 1.0 10–3 MC) 3.7 10–4 MD) 0E) none of these

67. Consider the reaction 3A + B + C D + E

where the rate law is defined as

– = k[A]2[B][C]

An experiment is carried out where [B]0 = [C]0 = 1.00 M and [A]0 = 2.49 10–4 M. After 2.72 min, [A] = 3.46 10–5 M. What is the value of k?

A) 4.38 10–7 L3/mol3 • sB) 2.14 10–5 L3/mol3 • sC) 1.52 102 L3/mol3 • sD) 9.15 103 L3/mol3 • sE) 7.61 107 L3/mol3 • s

68. Consider the reaction 3A + B + C D + E

where the rate law is defined as

– = (1.68 102 L3/mol3 • s)[A]2[B][C]

An experiment is carried out where [B]0 = [C]0 = 1.00 M and [A]0 = 2.50 10–4 M. What is the half-life for this experiment?

A) 7.44 10-7 sB) 2.38 101 sC) 4.12 10–3 sD) 1.68 102 sE) 1.25 10–5 s


Consider the reaction 3A + B + C D + E where the rate law is defined as

– = k[A]2[B][C] An experiment is carried out where [B]0 = [C]0 = 1.00 M and [A]0 = 1.00 10–4 M.

69. What is the concentration of C after 10.0 min?A) 1.00 MB) 1.10 10–5 MC) 0.330 MD) 0.100 ME) none of these

70. What is the concentration of A after 10.0 min?A) 1.06 10–9 MB) 2.38 10–6 MC) 9.80 10–6 MD) 1.27 10–5 ME) none of these

71. At a particular temperature, N2O5 decomposes according to a first-order rate law with a half-life of 3.0 s. If the initial concentration of N2O5 is 1.0 1016 molecules/cm3, what will be the concentration in molecules/cm3 after 10.0 s?A) 9.9 1014

B) 1.8 1012

C) 7.3 109

D) 6.3 103

E) 9.4 102

72. The reaction 3NO N2O + NO2

is found to obey the rate law Rate = k[NO]2. If the first half-life of the reaction is found to be 4.4 s, what is the length of the fourth half-life?

A) 8.3 sB) 18 sC) 70 sD) 26 sE) 66 s

73. In 6 M HCl, the complex ion Ru(NH3)63+ decomposes to a variety of products. The reaction is first order in Ru(NH3)6

3+ and has a half-life of 14 h at 25°C. Under these conditions, how long will it take for the [Ru(NH3)6

3+] to decrease to 53.0% of its initial value?A) 15 hB) 5.6 hC) 6.6 hD) 7.4 hE) 13 h

74. At a particular temperature, the half-life of a zero-order reaction is 19.0 min. How long will it take for the reactant concentration to be depleted by a factor of 8?A) 57.0 minB) 33.3 minC) 133 minD) 38.0 minE) 152 min

75. The elementary chemical reaction O + ClO Cl + O2

is made pseudo-first order in oxygen atoms by using a large excess of ClO radicals. The rate constant for the reaction is 3.5 10–11 cm3/molecule • s. If the initial concentration of ClO is 1.0 1011 molecules/cm3, how long will it take for the oxygen atoms to decrease to 10.% of their initial concentration?

A) 2.4 sB) 0.017 sC) 3.2 10–3 sD) 0.66 sE) 23 s


Two isomers (A and B) of a given compound dimerize as follows:

Both processes are known to be second order in reactant, and k1 is known to be 0.25 L/mol • s at 25° C, where

Rate = – = k1[A]2

In a particular experiment, A and B were placed in separate containers at 25° C, where [A] 0 = 1.0 10–2 M and [B]0 = 2.5 10–

2 M. It was found that [A] = 3[B] after the reactions progressed for 3.0 min.

76. Calculate the concentration of A2 after 3.0 min.A) 2.8 10–22 MB) 6.9 10–3 MC) 3.1 10–3 MD) 1.6 10–3 ME) none of these

77. Calculate the value of k2 where

Rate = – = k2[B]2

A) 2.2 L/mol • sB) 0.75 L/mol • sC) 1.9 L/mol • sD) 0.21 L/mol • sE) none of these

78. The reaction 2NO2 2NO + O2 obeys the rate law

= 1.40 10–2 [NO2]2 at 500° K.

If the initial concentration of NO2 is 1.00 M, how long will it take for the [NO2] to decrease to 25.0% of its initial value?

A)49.5 sB) 71.4 sC) 214 sD)1.40 10–2 sE) cannot be determined from these data

79. The following data were collected for the decay of HO2 radicals.Time [HO2] Time [HO2]0 s 1.0 1011 molec/cm3 14 s 1.25 1010 molec/cm3

2 s 5.0 1010 molec/cm3 30 s 6.225 109 molec/cm3

6 s 2.5 1010 molec/cm3

Which of the following statements is true?

A) The decay of HO2 occurs by a first-order process.B) The half-life of the reaction is 2 ms.C) A plot of ln [HO2] versus time is linear with a slope of –k.D) The rate of the reaction increases with time.E) A plot of 1/[HO2] versus time gives a straight line.

80. Consider the second-order reaction aA products (which has a first half-life of 22 s). If the concentration of A after 13.4 s is 0.46 M, determine the initial concentration of A.A) 0.69 MB) 0.18 MC) 0.36 MD) 0.26 ME) 0.74 M

81. The reaction 2A + B C

has the following proposed mechanism.

Step 1: A + B D (fast equilibrium)

Step 2: D + B E

Step 3: E + A C + B

If step 2 is the rate-determining step, what should be the rate of formation of C?

A) k[A]B) k[A]2[B]C) k[A]2[B]2

D) k[A][B]E) k[A][B]2


The following data were collected in two studies of the reaction below. A + 2B C + D

[B]0 = 5.0 M [B]0 = 10.0 MExperiment 1 Experiment 2

Time (s) [A] (M) 10-2 [A] (M) 10-2

0 10.0 10.020 6.67 5.0040 5.00 3.3360 4.00 2.5080 3.33 2.00

100 2.86 1.67120 2.50 1.43

82. Which of the following mechanisms could be correct for this reaction?A) A + B E (fast)

E + B C + D (slow)B) A + B E (fast)

E + A C + D (slow)C) A + A E (slow)

E + B C + D (fast)D) none of these

83. The rate law for a reaction is found to be Rate = k[A]2[B]. Which of the following mechanisms gives this rate law?I. A + B E (fast)

E + B C + D (slow)II. A + B E (fast)

E + A C + D (slow)III. A + A E (slow)

E + B C + D (fast)

A) I onlyB) II onlyC) IIID) two of theseE) none of these

84. The experimental rate law for the decomposition of nitrous oxide (N2O) to N2 and O2 is Rate = k[N2O]2. Two mechanisms are proposed:I. N2O N2 + O

N2O + O N2 + O2

II. 2N2O N4O2

N4O2 2N2 + O2

Which of the following could be a correct mechanism?

A) Mechanism I with the first step as the rate-determining step.B) Mechanism I with the second step as the rate-determining step.C) Mechanism II with the second step as the rate-determining step.D) Two of these could be correct.E) None of these could be correct.

85. What is the overall order of a reaction with the following rate law? Rate = [A] 2 [B] 1 [C] 0

A) 0B) 1C) 2D) 3 E) none of these


The following questions refer to the reaction 2A2 + B2 2C. The mechanism below has been proposed:step 1 (very slow) A2 + B2 R + Cstep 2 (slow) A2 + R C

86. What is the molecularity of step 2?A) unimolecularB) bimolecularC) termolecularD) quadmolecularE) The molecularity cannot be determined.

87. Which step(s) is(are) rate-determining?A) both stepsB) step 1C) step 2D) a step that is intermediate between step 1 and step 2E) none of these

88. According to the proposed mechanism, what should the overall rate law be?A) Rate = k[A2]2

B) Rate = k[A2][B2]C) Rate = k[A2][R]D) Rate = k[R]2

89. When ethyl chloride, CH3CH2Cl, is dissolved in 1.0 M NaOH, it is converted into ethanol, CH3CH2OH, by the reaction CH3CH2Cl + OH– CH3CH2OH + Cl–

At 25°C the reaction is first order in CH3CH2Cl, and the rate constant is 1.0 10–3 s–1. If the activation parameters are A = 3.4 1014 s–1 and Ea = 100.0 kJ/mol, what will the rate constant be at 28°C? (R = 8.314 J/mol • K)

A) 1.5 10–3 s–1

B) 8.9 102 s–1

C) 1.1 10–3 s–1

D) 9.2 10–3 s–1

E) 3.8 1014 s–1

90. The rate constant for a reaction increases from 10.0 s-1 to 100. s-1 when the temperature is increased from 317 K to 427 K. What is the activation energy for the reaction in kJ/mol? (R = 8.314 J/mol • K)A) 23.6 kJ/molB) 10.2 kJ/molC) 1.74 kJ/molD) 21.1 kJ/molE) 0.0756 kJ/mol

91. The activation energy for the reaction H2(g) + I2(g) 2HI(g) is changed from 184 kJ/mol to 59.0 kJ/mol at 600. K by the introduction of a Pt catalyst. Calculate the value of the ratio rate(catalyzed)/rate(uncatalyzed).A) 1.00B) 7.62 1010

C) 1.38D) 0.321E) none of these

92. Raw milk sours in 4.0 h at 28°C but takes 48 h to sour in a refrigerator at 5°C. Calculate the activation energy for the souring of milk.A) 75.2 kJB) 4.00 kJC) 12.0 kJD) 8.87 kJE) none of these

93. The reaction 2H2O2 2H2O + O2 has the following mechanism: H2O2 + I– H2O + IO–

H2O + IO– H2O + O2 + I–

What is the catalyst in the reaction?

A) H2OB) I–

C) H2O2

D) IO–

Answer Key1. F 11. E 21. A 31. D 41. B 51. C 61. D 71. A 81. E 91. B2. A 12. B 22. C 32. B 42. B 52. D 62. A 72. E 82. B 92. A3. A 13. A 23. A 33. B 43. A 53. A 63. E 73. E 83. B 93. B4. C 14. E 24. C 34. E 44. E 54. C 64. A 74. B 84. C5. B 15. A 25. E 35. A 45. E 55. B 65. D 75. D 85. D6. D 16. A 26. A 36. C 46. E 56. C 66. C 76. D 86. B7. A 17. A 27. A 37. B 47. A 57. B 67. C 77. A 87. B8. A 18. C 28. C 38. B 48. A 58. A 68. B 78. C 88. B9. C 19. A 29. C 39. A 49. A 59. B 69. A 79. E 89. A10. A 20. E 30. C 40. A 50. D 60. E 70. D 80. E 90. A

Practice Ch 15

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