ejercicios de cinética
Opción Múltiple
Elige la opción que complete mejor el enunciado o que responda mejor a la pregunta.
____
1. Of the following questions, which ones are thermodynamic rather than kinetic concepts?
I.
Can substances react when they are put together?
II.
If a reaction occurs, how fast will it occur?
III.
What is the mechanism by which the reaction occurs?
IV.
If substances react, what energy changes are associated with the reaction?
a.
b.
c.
d.
e.
____
I and III
II and IV
I and IV
II and III
I, III, and IV
2. Which of the following expressions does not represent a proper expression for the rate of this reaction?
2A + 3B  F + 2G
a.
b.
c.
d.
e.
____
3. One of the reactions that is used to produce gaseous hydrogen commercially follows. A proper expression for
the rate of this reaction could be ____.
H2O(g) + CO(g)  H2(g) + CO2(g)
a.
b. k
c.
d.
e.
____
4. In the following reaction, the rate of formation of NH3 is 0.15 mol/Lmin. What is the rate of reaction?
N2 + 3H2  2NH3
a.
b.
c.
d.
e.
____
0.15 mol/Lmin
0.075 mol/Lmin
0.20 mol/Lmin
0.30 mol/Lmin
0.075 mol/Lmin
5. In the following reaction,
= 0.89 mol/Ls. What is the value of the rate of the reaction at this time?
A + 3B  AB3
a.
b.
c.
d.
e.
2.67 mol/Ls
0.89 mol/Ls
0.30 mol/Ls
0.22 mol/Ls
0.30 mol/Ls
____
6. Consider the exothermic combustion of coal. Which of the following could increase the rate of reaction?
a. using smaller pieces of coal
b. increasing the concentration of oxygen
c. lowering the temperature
d. both (a) and (b) are correct
e. choices (a), (b) and (c) are all correct
____
7. Suppose a reaction A + B  C occurs at some initial rate at 25C. Which response includes all of the changes
below that could increase the rate of this reaction?
I.
lowering the temperature
II.
adding a catalyst
III.
increasing the initial concentration of B
a.
b.
c.
d.
e.
I
II
III
I and II
II and III
____
8. Which response below is not an example of how the nature of reactants affects the rate of reaction?
a. Magnesium reacts faster in higher concentrations of HCl(aq).
b. Graphite burns faster than diamond under equal conditions.
c. Calcium reacts faster in water than magnesium.
d. White phosphorus reacts explosively on contact with air; red phosphorus does not.
e. Coal dust burns faster than large chunks of coal.
____
9. Which of the following reactions would be expected to be the slowest?
a. Pb2+(aq) + CrO42(aq)  PbCrO4(s)
b. CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)
c. Ag+(aq) + Cl(aq)  AgCl(s)
d. H+(aq) + OH(aq)  H2O
e. H+(aq) + CN(aq)  HCN(aq)
____ 10. For a given reaction, the rate-law expression is ____.
a. an equation in which reaction rate is equal to a mathematical expression involving, or
related to, concentrations of reactants involved in the rate-determining step
b. an equation that gives the additional energy that reactants must obtain in order to react
c. a constant of proportionality between reaction rate and the concentrations of reactants
d. the sum of the powers to which reactant concentrations appear
e. 55 miles per hour
____ 11. The gas phase reaction A + B  C has a reaction rate which is experimentally observed to follow the
relationship rate = k[A][B]2. The overall order of the reaction
a. is third.
b. is zero.
c. cannot be determined.
d. is first.
e. is second.
____ 12. The gas phase reaction A + B + C  D has a reaction rate which is experimentally observed to follow the
relationship rate = k[A]2[C]. The reaction is ____ order in A, ____ order in B, and ____ order in C.
a. second; zero; zero
b. second; zero; first
c. second; first; zero
d. first; second; third
e. first; second; zero
____ 13. The gas phase reaction A + B  C has a reaction rate which is experimentally observed to follow the
relationship rate = k[A]2[B]. Which one of the following would affect the value of the specific rate constant,
k?
a. changing the concentration of C
b. changing the concentration of A
c. changing the concentration of B
d. increasing the temperature
e. all of these
____ 14. A hypothetical reaction X + 2Y  Products is found to be first order in X and second order in Y. What are
the units of k, the specific rate constant, if reaction rate is expressed in units of moles per liter per second?
a. M3s
b. M1s
c. Ms1
d. M2s1
e. M2s1
____ 15. Which of the following statements regarding the rate constant in the rate law expression is incorrect?
a. Its value increases with temperature.
b. Its units depend on the overall order of reaction.
c. Its value is independent of initial concentration at a given temperature.
d. Its value is experimentally determined.
e. The larger its value, the slower the reaction rate.
____ 16. A reaction A + 2B  C is found to be first order in A and first order in B. What are the units of the rate
constant, k, if the rate is expressed in units of moles per liter per minute?
a. Mmin1
b. M
c. M1min1
d. M2min1
e. min1
____ 17. Consider the following rate law expression: rate = k[A]2[B]. Which of the following is not true about the
reaction having this expression?
a. The reaction is first order in B.
b. A and B must both be reactants.
c. Doubling the concentration of A doubles the rate.
d. The reaction is second order in A.
e. The reaction is overall third order.
____ 18. The gas phase reaction A + B  C has a reaction rate which is experimentally observed to follow the
relationship rate = k[A]2[B]. If the concentration of A is tripled and the concentration of B is doubled, the
reaction rate would be increased by a factor of ____.
a. 18
b. 9
c. 12
d. 36
e. 6
____ 19. The gas-phase reaction
2NO + 2H2  N2 + 2H2O
has the following rate law expression, rate = k[NO]2[H2]. If the [NO] is halved and the [H2] is tripled, what
change in rate is expected?
a. decrease by 3/4
b. decrease by 3/2
c. increase by 3/4
d. increase by 3/2
e. stays same
____ 20. The gas-phase reaction
2NO + 2H2  N2 + 2H2O
has the following rate law expression, rate = 0.14 L2/mol2s[NO]2[H2]. If the [NO] is 0.95 M and the [H2] is
0.45 M, what rate is expected?
a. 0.060 mol/Ls
b. 0.027 mol/Ls
c. 1.54 mol/Ls
d. 0.43 mol/Ls
e. 0.057 mol/Ls
____ 21. A reaction is second order in X and zero order in Y. Doubling the initial concentration of X and halving the
initial concentration of Y at constant temperature causes the initial rate to
a. be undeterminable without the balanced equation.
b. remain unchanged.
c. increase by a factor of 2.
d. decrease by a factor of 2.
e. increase by a factor of 4.
____ 22. Consider the following rate data for the reaction below at a particular temperature.
2A + 3B  Products
Experiment
Initial [A]
Initial [B]
Initial Rate of Loss of A
1
2
3
0.10 M
0.10 M
0.20 M
7.20  105 Ms1
1.44  104 Ms1
8.64  104 Ms1
0.30 M
0.60 M
0.90 M
The reaction is ____ order in A and ____ order in B.
a. first; second
b. first; first
c. third; first
d. second; second
e. second; first
____ 23. Given the following data for the reaction below.
NH4+ + NO2  N2 + 2H2O
Trial
1
2
3
[NH4+]
0.010 M
0.015
0.010
[NO2]
0.030 M
0.030
0.015
Rate
0.020 M/s
0.030
0.005
The rate law for the reaction is
a. rate = k[NH4+]2[NO2]
b. rate = k[NH4+][NO2]
c. rate = k[NH4+][NO2]2
d. rate = k[NH4+]2[NO2]2
e. None of these
____ 24. Determine the rate-law expression for the reaction below:
2A + B2 + C  B + BC
Trial
1
2
3
4
a.
b.
c.
d.
e.
Initial [A]
0.20 M
0.40 M
0.20 M
0.20 M
Initial [B2]
0.20 M
0.30 M
0.30 M
0.40 M
Initial [C]
0.20 M
0.20 M
0.20 M
0.40 M
Initial Rate of Formation of BC
2.4  106 Mmin1
9.6  106 Mmin1
2.4  106 Mmin1
4.8  106 Mmin1
rate = k[A][C]2
rate = k[A]2[B2][C]
rate = k[B2]2[C]2
rate = k[A][B2][C]
rate = k[A]2[C]
____ 25. Rate data have been determined at a particular temperature for the overall reaction
2NO + 2H2  N2 + 2H2O
in which all reactants and products are gases.
Trial Run
1
2
3
Initial [NO]
0.10 M
0.10 M
0.20 M
Initial [H2]
0.20 M
0.30 M
0.20 M
Initial Rate (Ms1)
0.0150
0.0225
0.0600
The rate-law expression is ____.
a. rate = k[NO]2[H2]2
b. rate = k[NO][H2]
c. rate = k[NO][H2]2
d. rate = k[NO]2[H2]
e. None of these is correct.
____ 26. A troublesome reaction that is responsible in part for acid rain is
SO3 + H2O  H2SO4
Rate data have been determined at a particular temperature for the reaction in which all reactants and products
are gases.
Trial Run
1
2
3
4
Initial [SO3]
0.35 M
0.70 M
0.35 M
0.70 M
Initial [H2O]
0.35 M
0.35 M
0.70 M
0.70 M
Initial Rate (Ms1)
0.150
0.600
0.300
1.20
The rate-law expression is ____.
a. rate = k[SO3]2
b. rate = k[SO3]2[H2O]
c. rate = k[SO3][H2O]2
d. rate = k[SO3][H2O]
e. rate = k[SO3]2[H2O]2
____ 27. NO reacts with chlorine in a gas phase reaction to form nitrosyl chloride, NOCl. From the following
experimental data, determine the form of the equation that describes the relationship of reaction rate to initial
concentrations of reactants.
2NO + Cl2  2NOCl
Run
1
2
3
a.
b.
c.
d.
e.
Initial [NO]
0.50 M
1.00 M
1.00 M
Initial [Cl2]
0.50 M
1.00 M
0.50 M
Initial Rate of Formation of NOCl
1.14 M/hr
9.12 M/hr
4.56 M/hr
rate = k[NO]2
rate = k[NO][Cl2]
rate = k[NO]
rate = k[NO]2[Cl2]2
rate = k[NO]2[Cl2]
____ 28. The following data were collected for the following reaction at a particular temperature. What is the rate-law
expression for this reaction? rate = ____.
A+BC
Experiment
1
2
3
Initial [A]
0.10 M
0.20 M
0.10 M
Initial [B]
0.10 M
0.20 M
0.20 M
Initial Rate of Formation of C
4.0  104 M/min
3.2  103 M/min
1.6  103 M/min
a.
b.
c.
d.
e.
k[A][B]
k[A]2
k[A][B]2
k[A]
k[B]
____ 29. The following data were collected for the following reaction at a particular temperature. What is the rate-law
expression for this reaction? rate = ____.
NH3 + O2  N2O + H2O
Experiment
1
2
3
a.
b.
c.
d.
e.
Initial [NH3]
1.10 M
2.20 M
1.10 M
Initial [O2]
1.10 M
2.20 M
2.20 M
Initial Rate
5.5  103 M/s
4.4  102 M/s
2.2  102 M/s
k[NH3][O2]
k[NH3]
k[NH3]2
k[NH3][O2]2
k[O2]
____ 30. Determine the rate-law expression for the reaction below at the temperature at which the tabulated initial rate
data were obtained. rate = ____
A + 2B + 3C  Products
Experiment
1
2
3
4
a.
b.
c.
d.
e.
Initial [A]
0.10 M
0.40 M
0.20 M
0.20 M
Initial [B]
0.20 M
0.20 M
0.20 M
0.40 M
Initial [C]
0.10 M
0.10 M
0.25 M
0.10 M
Initial Rate of Loss of A
4.0  102 Mmin1
4.0  102 Mmin1
1.0  101 Mmin1
1.6  101 Mmin1
k[C]2
k[B]2[C]
k[A][B]
k[A]2[C]
none of these
____ 31. Evaluate the specific rate constant for this reaction at 800C. The rate-law expression is rate = k[NO]2[H2].
(Choose the closest answer.)
2NO(g) + 2H2(g)  N2(g) + 2H2O(g)
Experiment
1
2
3
a.
b.
c.
d.
Initial [NO]
0.0010 M
0.0040 M
0.0040 M
4.6 M2s1
0.024 M2s1
1.3  102 M2s1
22 M2s1
Initial [H2]
0.0060 M
0.0060 M
0.0030 M
Initial Rate of Reaction (Ms1)
7.9  107
1.3  105
6.4  106
e. 0.82 M2s1
____ 32. Evaluate the specific rate constant at the temperature at which the data were collected. The rate-law
expression is rate = k[NO]2[H2].
H2(g) + NO(g)  N2O(g) + H2O(g)
Experiment
1
2
3
a.
b.
c.
d.
e.
Initial [NO] (M)
0.30
0.60
0.60
Initial [H2] (M)
0.35
0.35
0.70
Initial Rate (Ms1)
2.835  103
1.134  102
2.268  102
2.7  102 M2s1
9.0  102 M2s1
8.1  103 M2s1
1.6  104 M2s1
9.4  103 M2s1
____ 33. Rate data have been determined at a particular temperature for the overall reaction
2NO + 2H2   + 2H2O
in which all reactants and products are gases. The value of the specific rate constant at this temperature is
____.
Trial Run
1
2
3
a.
b.
c.
d.
e.
Initial [NO]
0.10 M
0.10 M
0.20 M
Initial Rate (Ms1)
0.0150
0.0225
0.0600
Initial [H2]
0.20 M
0.30 M
0.20 M
7.5 M2s1
375 M2s1
3.0  103 M2s1
3.0  104 M1s1
0.75 M1s1
____ 34. Consider a chemical reaction involving compounds A and B, which is found to be first order in A and second
order in B. At what rate will the reaction occur in experiment 2?
Experiment
1
2
a.
b.
c.
d.
e.
Rate (Ms1)
0.10
?
Initial [A]
1.0 M
2.0 M
Initial [B]
0.20 M
0.60 M
1.8 Ms1
0.36 Ms1
0.60 Ms1
1.2 Ms1
0.20 Ms1
____ 35. The oxidation of NO by O3 is first order in each of the reactants, and its rate constant is 1.5  107 M1s1. If
the concentrations of NO and O3 are each 5.0  107 M, what is the rate of oxidation of NO in Ms1?
a. 7.5  107
b. 15
c. 3.8  106
d. 2.5  1014
e. 7.5
____ 36. A bimolecular reaction is found to be 1st order with respect to both reactants. If the rate of reaction is 1.87
mol/L s at 25C, what is the reaction rate if both reactant concentrations are doubled?
a. 0.94 mol/Ls
b. 46.8 mol/Ls
c. 7.48 mol/Ls
d. 1.87 mol/Ls
e. 3.74 mol/Ls
____ 37. Consider the hypothetical reaction and rate data below. Determine the form of the rate-law expression (i.e.,
determine the values of a and b in rate = k[A]a[B]b) and also the value of the specific rate constant, k. Which
of the answers below would be the initial rate of reaction for [A]initial = 0.40 M and [B]initial = 0.10 M?
3A + 2B  Products
Run
1
2
3
a.
b.
c.
d.
e.
[A]initial
0.10 M
0.20 M
0.30 M
[B]initial
0.10 M
0.30 M
0.10 M
Initial Rate of Reaction
(moles per liter per second)
4.0  104
4.8  103
3.6  103
1.6  104 Ms1
6.4  103 Ms1
3.4  103 Ms1
1.2  103 Ms1
4.8  104 Ms1
____ 38. The half-life for the reactant A in the first order reaction below is 36.2 seconds. What is the rate constant for
this reaction at the same temperature?
A  B
a.
b.
c.
d.
e.
52.2 s1
0.00832 s1
18.1 s1
0.0276 s1
0.0191 s1
____ 39. The rate constant for the first order reaction below is k = 3.3  102 min1 at 57 K. What is the half-life for this
reaction at 57 K?
A  B + C
a.
b.
c.
d.
e.
1200 min
30 min
21 min
9.1 min
61 min
____ 40. The rate constant for the second order reaction below is 2.79 L/mol min at 48C. If the initial concentration
of NO2 is 1.05 M , what is the half-life?
2NO2  N2O4
a.
b.
c.
d.
e.
14.9 s
20.5 s
176 s
10.3 s
0.341 min
____ 41. The half-life of the zero order reaction below is 0.56 minutes. If the initial concentration of A is 3.4 M, what
is the rate constant?
AB
a.
b.
c.
d.
e.
6.07 mol/Lmin
1.79 mol/Lmin
3.04 mol/Lmin
1.24 mol/Lmin
0.619 mol/Lmin
____ 42. The decomposition of dimethylether at 504C is first order with a half-life of 1570. seconds. What fraction of
an initial amount of dimethylether remains after 4710. seconds?
a. 1/6
b. 1/8
c. 1/32
d. 1/16
e. 1/3
____ 43. A molecule of ethyl alcohol is converted to acetaldehyde in one's body by zero order kinetics. If the
concentration of alcohol is 0.015 mol/L and the rate constant = 6.4  105 mol/Lmin, what is the
concentration of alcohol after 3.5 hours?
a. 0.15 mol/L
b. 0.0032 mol/L
c. 9.6  107 mol/L
d. 0.0016 mol/L
e. 4.3  103 mol/L
____ 44. A chemical reaction (below) is first order in A and has a rate constant of 1.2  103 min1. If the initial
concentration of A is 0.40 M., how much time must pass in order to reduce the concentration of A to 0.22 M?
A  B + C
a.
b.
c.
d.
e.
3.0  102 min
7.4  103 min
2.2  102 min
4.3  104 min
5.0  102 min
____ 45. The gas phase reaction below obeys the rate-law expression rate = k[SO2Cl2]. At 593 K the specific rate
constant is 2.2  105 s1. A 2.0-g sample of SO2Cl2 is introduced into a closed 4.0-L container.
SO2Cl2  SO2 + Cl2
How much time must pass in order to reduce the amount of SO2Cl2 present to 1.8 grams?
a. 2.1  102 seconds
b. 5.8  104 seconds
c. 4.8  103 seconds
d. 3.5  102 seconds
e. 7.4  103 seconds
____ 46. The gas phase reaction below obeys the rate-law expression rate = k[PCl5]. At 400 K the specific rate constant
is 0.0371 min1. How many hours are required to reduce a sample of PCl5 to 10% of its original amount?
PCl5  PCl3 + Cl2
a.
b.
c.
d.
e.
186 hrs
3.10 hrs
62 hrs
3.71 hrs
1.03 hrs
____ 47. Consider the following first order reaction.
A2B  AB + A
If it takes 87 seconds for the concentration of A2B to be reduced from 2.2 M to 0.12 M, what is the value of
the specific rate constant?
a. 18.3 min1
b. 2.01 s1
c. 0.0334 min1
d. 3.51  103 s1
e. 2.01 min1
____ 48. The reaction below has the following rate law: rate = 0.011 L/mols [SF4]2.
SF4  SF2 + F2
How many minutes will it take for the concentration of SF4 to be reduced from 2.5 M to 0.25 M?
a. 0.025 min
b. 22.7 min
c. 5.5 min
d. 0.040 min
e. 327 min
____ 49. At 300 K the reaction below obeys the rate law Rate = k[NOCl]2 where k = 2.8  105 M1s1.
2NOCl  2NO + Cl2
Suppose 1.0 mole of NOCl is introduced into a 2.0-liter container at 300 K. Evaluate the half-life of the
reaction.
a. 1.1  103 seconds
b. 2.4  104 seconds
c. 4.0  104 seconds
d. 3.6  104 seconds
e. 2.6  103 seconds
____ 50. The second order reaction below has a rate constant of 5.76 M1min1 at 1600 K.
2CH4  C2H2 + 3H2
How long would it take for the concentration of CH4 to be reduced from 0.89 M to 5.25  104 M?
a. 5.51 hrs
b. 9.27 hrs
c. 2.75 hrs
d. 0.15 hrs
e. 165 hrs
____ 51. Compounds A and B react to form C and D in a reaction that is found to be second-order overall and
second-order in B. The rate constant at 50.C is 2.48 liter per mole per minute. What is the half-life of B (in
min) if 0.822 M B reacts with excess A?
A+BC+D
a.
b.
c.
d.
e.
5.88
0.491
0.0139
12.0
1.39
____ 52. At 100 K the reaction below obeys the rate law rate = k[AB2]2 where k = 5.7 M1s1.
2AB2  A2 + 2B2
What would the concentration of AB2 be after 60 minutes if the initial concentration was 1.45 mol/L?
a. 2.4  105 M
b. 4.9  105 M
c. 1.9  104 M
d. 1.2  102 M
e. 2.0  105 M
____ 53. At a certain temperature the reaction below obeys the rate-law expression rate = (1.14  103 M1s1)[B]2. If
5.00 mol of B is initially present in a 1.00-L container at that temperature, how long would it take for 2.00
mol of B to be consumed at constant temperature?
2B  C + D
a.
b.
c.
d.
e.
58.5 s
224 s
46.0 s
87.5 s
73.0 s
____ 54. Compounds A and B react to form C and D in a reaction that is found to be second-order overall and
second-order in B. The rate constant at 30C is 0.622 liter per mole per minute.
A+BC+D
How many minutes does it take 4.0  102 M B (mixed with excess A) to be reduced to 3.3  102 M B?
a. 3.6 min
b. 5.0 min
c. 6.4 min
d. 1.4 min
e. 8.5 min
____ 55. A plot of
a.
b.
c.
d.
e.
versus time is linear for the reaction D  E. What is the kinetic order of the reaction?
one-half
negative one
first
zero
second
____ 56. A plot of ln [C] versus time is linear for the reaction C  D. What is the kinetic order of the reaction?
a. one-half
b. zero
c. second
d. negative one
e. first
____ 57. Which statement is incorrect?
a. The rate law expression relates rate and concentration.
b. The integrated rate equation relates time and concentration.
c. The specific rate constant for a zero-order reaction is independent of temperature.
d. The half-life for a first-order reaction is independent of initial concentrations.
e. The reaction rate for a zero-order reaction is independent of concentrations.
____ 58. Which idea listed below is not a part of the collision theory of reaction rates?
a. Molecules must be properly oriented when they collide to react.
b. All molecular collisions result in a reaction.
c. Molecules must collide to react.
d. Molecules must collide with enough kinetic energy to overcome the potential energy
stabilization of the bonds.
e. Effective collisions result in a chemical reaction.
____ 59. Which one of the following statements is false?
a. The transition state is a short-lived, high energy state, intermediate between reactants and
products.
b. A catalyst alters the rate of a reaction and is neither a product nor a reactant in the overall
equation.
c. In reactions that are second order in one reactant and first order in another, the slow step
generally involves a three-body collision of these reactants.
d. According to collision theory a three-body collision is less likely than a two-body
collision.
e. In order for a reaction to occur, reactant molecules must collide with each other.
____ 60. Which of the following statements regarding collision and transition state theory is false?
a. All reactant collisions result in product formation.
b. Reactants must collide to form products.
c. Activation energy is always positive.
d. Reactant molecules must absorb energy to form the transition state.
e. Reactant collisions must be oriented properly to form products.
____ 61. Which term is incorrectly matched with its description?
a. Transition State / short-lived high-energy intermediate state
b. Endothermic Reaction / reaction having Ea, reverse > Ea, forward
c. Activation Energy / kinetic energy required for reaction to occur
d. Effective Collision / molecular collision resulting in a reaction
e. Net energy change of the reaction / Ea, forward  Ea, reverse
____ 62. A reaction has an activation energy of 40 kJ and an overall energy change of reaction of 100 kJ. In each of
the following potential energy diagrams, the horizontal axis is the reaction coordinate and the vertical axis is
potential energy in kJ. Which potential energy diagram best describes this reaction?
a.
b.
c.
d.
e.
Exhibit 16-1
Given the following potential energy diagram for the one-step reaction
X+YZ+R
____ 63. Refer to Exhibit 16-1. The reaction ____.
a. releases energy
b. occurs without a net change in energy
c. is impossible
d. may either absorb or release energy
e. absorbs energy
____ 64. Refer to Exhibit 16-1. The arrow "d" represents the ____.
a. the net change in energy for the reaction
b. energy content of reactants
c. activation energy for the reverse reaction
d. energy content of products
e. activation energy for the forward reaction
____ 65. Refer to Exhibit 16-1. The point "b" represents ____.
a. the energy of the mixture when half of the reactants have been converted to products
b. the energy of the forward reaction
c. the energy of the reverse reaction
d. the energy of the transition state
e. the number of moles of transition state that must be formed
____ 66. Refer to Exhibit 16-1. The activation energy of the reverse reaction is equal to ____.
a. "a" plus "c"
b. "d" minus "a"
c. "d"
d. "c"
e. "c" plus "d"
____ 67. Refer to Exhibit 16-1. The arrow "a" represents the ____.
a. the net change in energy for the reaction
b. activation energy for the reverse reaction
c. energy content of reactants
d. activation energy for the forward reaction
e. energy content of products
____ 68. Given the following potential energy diagram for the one-step reaction
X+YZ+R
The arrow "c" represents the ____.
a. activation energy for the forward reaction
b. energy content for the reaction
c. activation energy for the reverse reaction
d. net energy of reaction for the forward reaction
e. net energy of reaction for the reverse reaction
____ 69. Which of the following statements about reaction mechanisms is false?
a. Reaction mechanisms involve complex reaction steps.
b. A reaction can have more than one possible mechanism.
c. A reaction mechanism must be consistent with the experimentally observed rate law.
d. The slowest step in the reaction mechanism is called the rate-determining step.
e. Reaction mechanisms are difficult to prove.
____ 70. A reaction mechanism will usually be
a. obvious from a consideration of the reaction rate data.
b. generally obvious from the balanced chemical equation.
c. the only possible explanation for the reaction.
d. obvious from a consideration of the balanced chemical equation.
e. difficult to verify experimentally.
____ 71. Which of the following is a kinetics concept?
a. reaction mechanism
b. enthalpy
c. entropy
d. spontaneity
e. free energy
____ 72. Consider the hypothetical reaction shown below.
A + 2B  AB2
Assume that the following proposed mechanism is consistent with the rate data.
B
B2
B
A
+
+
+
+
B  B2
A  AB + B
AB  AB2
2B  AB2
slow
fast
fast
overall
Which one of the following statements must be true? The reaction is ____.
a. first order in A, second order in B, and third order overall
b. second order in A and second order overall
c. first order in A and first order overall
d. second order in B and second order overall
e. second order in B, zero order in A, and third order overall
____ 73. Consider the hypothetical reaction shown below.
2A + C2  A2C + C
Assume that the following proposed mechanism is consistent with the rate data.
A
AC
2A
+
+
+
C2  AC + C
A  A2C
C2  A2C + C
slow
fast
overall
Which one of the following statements must be true? The reaction is ____.
a. second order in C2 and second order overall
b. second order in A and second order overall
c. first order in A, first order in B, and third order overall
d. second order in C2, zero order in A, and third order overall
e. first order in A and first order in C2
____ 74. Consider the following proposed mechanism. If this mechanism for the overall reaction were correct, and if k1
were much less than k2, then the observed rate law would be
2A
C+I
I+B
a.
b.
c.
d.
e.
C+D
rate = k1[A]2  k2[C][D]
rate = k1k2[A]2[I][B]
rate = k1[A]
rate = k1[A]2
rate = k2[I][B]
____ 75. Suppose the reaction
2AB + C2  A2C + B2C
occurs by the following mechanism.
Step 1
Step 2
Step 3
Step 4
Overall
AB
B
AC2
A2C2
2 AB
+
+
+
+
+
C2  AC2
AB  AB2
AB2  A2C2
B2  A2C
C2  A2C
+
B
+
+
+
B2
B2C
B2C
slow
fast
fast
fast
The rate law expression must be rate = ____.
a. k[AB]2
b. k[AB]2[C2]
c. k[AB]
d. k[AB][C2]
e. k[C2]
____ 76. Assume the following reaction occurs by the given reaction mechanism.
3H2 + CO  CH4 + H2O
Step 1
Step 2
Step 3
Overall
H2
H2
H2
3H2
+
+
+
+
CO  H2CO
H2CO  CH4
O  H2O
CO  CH4
slow
fast
fast
+O
+ H2O
The rate law expression must be rate = ____.
a. k[H2][CO]2
b. k[H2]2[CO]2
c. k[H2]2[CO]
d. k[H2]2[CO]3
e. k[H2][CO]
____ 77. Consider the reaction below and its observed rate law expression. Which proposed mechanisms are
consistent with the rate law expression?
rate = k[NO2]2
2NO2  2NO + O2
I.
NO2 + NO2  N2O4
N2O4  N2 + 2O2
N2 + O2  2NO
2NO2  2NO + O2
slow
fast
fast
overall
II.
NO2  N + O2
NO2 + N  N2O2
N2O2  2NO
2NO2  2NO + O2
slow
fast
fast
overall
III.
NO2  NO + O
O + NO2  NO + O2
2NO2  2NO + O2
slow
fast
overall
a.
b.
c.
d.
e.
I
II
III
I and III
another combination
____ 78. Which statement concerning a possible mechanism for a reaction is false?
a. Each elementary step is represented by a balanced equation.
b. The elementary steps must add to give the equation for the overall reaction.
c. The speed of the slow step limits the rate at which the overall reaction occurs.
d. A possible mechanism must be consistent with the experimental data.
e. The slow step will only include reactants listed in the overall chemical equation.
____ 79. Which of the following statements concerning a reaction and its mechanism is false?
a. Reactions involving simultaneous trimolecular collisions are very common in gases.
b. A reaction intermediate is formed in early steps and completely consumed in later steps.
c. For a multi-step mechanism, the slowest step has the highest activation energy.
d. For a reactant, more is consumed than is formed.
e. For a product, more is formed than is consumed.
____ 80. Suppose the activation energy of a certain reaction is 250 kJ/mol. If the rate constant at T1 = 300 K is k1, and
the rate constant at T2 = 320 K is k2, then k2/k1 = ____. (The universal gas constant = 8.314 J/molK.)
a.
b.
c.
d.
e.
3  1029
3  1028
15.0
525
0.067
____ 81. The specific rate constant, k, for a reaction is 0.44 s1 at 298 K, and the activation energy is 245.kJ/mol.
Calculate k at 398 K. (The universal gas constant = 8.314 J/molK.)
a.
b.
c.
d.
e.
8.32  108 s1
2.71  1010 s1
1.03  1010 s1
6.17  1010 s1
4.51  109 s1
____ 82. The rate constant for a first-order reaction is 0.58 s1 at 25C. At what temperature would the rate constant
have a value of 0.75 s1? The activation energy is 84 kJ/mol and the universal gas constant = 8.314 J/molK.
a.
b.
c.
d.
e.
30C
310 K
298 K
300K
301 K
____ 83. The rate constant, k, for a first-order reaction is 1.36  103 s1 at 90.C and the activation energy is 78.4
kJ/mol. Calculate the rate constant for this reaction at 50.C.
a. 23.8 s1
b. 1.78  103 s1
c. 4.85 s1
d. 60.4 s1
e. 54.5 s1
____ 84. Calculate the activation energy of a reaction if the rate constant is 0.75 s1 at 25C and 11.5 s1 at 75C.
a. 20.4 kJ/mol
b. 15.8 kJ/mol
c. 31.4 kJ/mol
d. 47.1 kJ/mol
e. 681 J/mol
____ 85. A catalyst
a. lowers S for the process.
b. increases the amount of products present at equilibrium.
c. increases the rate at which equilibrium is reached without changing the equilibrium
constant.
d. increases the rate at which equilibrium is reached but decreases the equilibrium constant.
e. increases H for the process.
____ 86. Which of the following statements about catalysts are false?
a. Catalyst are often transition metals and transition metal oxides.
b. A catalyst lowers the activation energy.
c. A catalyst can make a nonspontaneous reaction spontaneous.
d. A catalyst speeds up both the forward and reverse reaction.
e. A catalyst speeds up the rate of reaction.
____ 87. Which of the following is not an example of an important, useful reaction catalyzed by transition metals
and/or their oxides?
a. the hydrogenation of unsaturated hydrocarbons
b. the Haber process for the production of ammonia
c. the chlorination of benzene
d. the contact process for the production of sulfur trioxide in producing sulfuric acid
e. the reaction of leaded fuels with the catalysts in catalytic converters
____ 88. The catalytic converters installed in newer models of automobiles are designed to catalyze certain kinds of
favorable reactions. Unfortunately, other unfavorable reactions also are catalyzed. Which one of those listed
below, all of which are catalyzed in such mufflers, is an unfavorable reaction?
a. 2C8H18(g) + 25O2(g)  16CO2(g) + 18H2O(g)
b. 2NO(g)  N2(g) + O2(g)
c. 2SO2(g) + O2(g)  2SO3(g)
d. 2CO(g) + O2(g)  2CO2(g)
e. C(s) + O2(g)  CO2(g)
____ 89. Which statement concerning biological catalysts is false?
a. Discovery or synthesis of catalysts that mimic the efficiency of naturally occurring
enzymes would saved on the costs of using high temperature and high pressure in
commercial processes.
b. Enzyme-catalyzed reactions are important examples of zero-order reactions.
c. Enzymes are proteins that act as catalysts for specific biochemical reactions.
d. Each enzyme catalyzes many different reactions in a living system.
e. The reactants in enzyme-catalyzed reactions are called substrates.
____ 90. The reaction, A + 2B  B2 + A, proceeds by the following mechanism: (A is a catalyst.)
(slow)
A + B  AB
(fast)
AB + B  B2 + A
What is the rate law expression for this reaction?
a. Rate = k[B]
b. Rate = k[A]2[B]
c. Rate = k[A][B]2
d. Rate = k[A]
e. Rate = k[A][B]
____ 91. For which of the following hypothetical rate laws would the units of the rate constant have the general form
Mtime?
a. rate = k[A]2
b. rate = k[A]4
c. rate = k[A]
d. rate = k[A]3
e. rate = k
____ 92. For a certain reaction, a plot of reactant concentration as a function of time gave a straight line.
What is the order of this reaction?
a. Second order
b. Zero order
c. Impossible to tell from the given information
d. Pseudo-first order
e. First order
____ 93. For a reaction to take place, the molecules that are reacting ______.
a. must have more energy than the products
b. must have less energy than the products
c. must be in considerable numbers
d. must be able to reach the activation energy
____ 94. In a reaction coordinate diagram, reacting molecules are most unstable ______.
a. when they are about to collide
c. right after they collide
b. at their initial position
d. at the transition state
____ 95. If the half-life of a reaction is independent of concentration, the reaction is:
a. Second order
b. First and second order
c. First order
d. Zero order
e. Zero and first order
____ 96. For the gas phase decomposition of dinitrogen pentoxide at 335K: 2 N2O5  4NO2 + O2
The average rate of disappearance of N2O5 over the time period from t = 0s to t = 114s is found to be
5.02 x 10-4 M s-1. The average rate of formation of NO2 over the same time period is:
a. 5.02 x 10-4 Ms-1
b. 2.01 x 10-3 Ms-1
c. 1.99 x 10-1 Ms-1
d. 2.51 x 10-4 Ms-1
e. 1.00 x 10-3 Ms-1
Use the initial rate data below to answer the following questions:
The following initial rate data are for the reaction of hypochlorite ion with iodide ion in 1M aqueous
hydroxide solution: OCl- + I-  OI- + ClExperiment
[OCl-]
[I-]
Rate
1
3.48 x 10-3
5.05 x 10-3
1.34 x 10-3
2
3.48 x 10-3
1.01 x 10-2
2.68 x 10-3
3
4
6.97 x 10-3
6.97 x 10-3
5.05 x 10-3
1.01 x 10-2
2.68 x 10-3
5.36 x 10-3
____ 97. What is the rate law for this reaction?
a. Rate = k[OCl-][I-]2
b. Rate = k[OCl-][I-]
c. Rate = k[OCl-]2[I-]
d. Rate = k[OCl-]
e. Rate = k[I-]
____ 98. What is the rate of the above reaction when [OCl-] = 0.224M and [I-] = 0.125M?
a. 0.267 Ms-1 b. 0.478 Ms-1 c. 0.367 Ms-1 d. 17.1 Ms-1
e. 2.13 Ms-1
____ 99. The gas phase decomposition of dimethyl ether at 500oC
CH3OCH3(g)  CH4(g) + H2(g) + CO)g)
is first order in CH3OCH3 with a rate constant of 4.00 x 10-4 s-1. If an experiment is performed in
which the initial concentration of CH3OCH3 is 4.56 x 10-2M, what is the concentration of CH3OCH3
after 4879 s have passed?
a. 0.0191 M
b. 0.00539 M c. 0.00648 M d. 0.0149 M
e. 0.0321 M
Use the information below to answer the following questions:
The concentration of A was found as a function of time during the course of the reaction: A  C,
and the data was graphed several different ways:
Time, s
0
1
2
3
4
5
6
7
8
[A], mol/L
0.9101
0.1893
0.1056
0.07327
0.05608
0.04542
0.03817
0.03291
0.02893
____ 100. What is the value of the rate constant, k, for the above reaction?
a. 4.18
b. 0.441
c. 0.431
d. 4.46
____ 101. Using the information above, what is the order of the reaction?
e. 0.455
a.
b.
c.
d.
e.
Zero order
Third order
Second order
Pseudo-first order
First order
____ 102. The mechanism below has been proposed for the hydrolysis of methyl acetate:
Which species in the above reaction mechanism is acting as a catalyst?
a. H3O+
b.
c.
d.
e. H2O
____ 103. For the gas phase decomposition of ethyl chloroformate, ClCOOC2H5  C2H5Cl + CO2
The rate constant has been determined at several different temperatures. When the data is graphed
as ln k vs. 1/T, the slope of the line is -1.48 x 104 and the y-intercept is 24.6.
What is the activation energy, Ea, for this reaction?
a. 9.62 kJ
b. 123 kJ
c. 1214 kJ
d. 205 kJ
e. 15.0 kJ
____ 104. Which of the following is a kinetic quantity?
a. rate of reaction
b. entropy
c. internal energy
d. free energy
e. enthalpy
____ 105. Which is not an example of the effect of subdivision of the reactant on the rate of chemical reaction?
a. A container of flammable liquid will burn on the surface but allowed to vaporize will burn
explosively.
b. The Grand Canyon was created by dissolution by water over millions of years.
c. Violent explosions that occur in grain elevators.
d. Some metals may be fused (welded) with minimal loss while their powders will burn in a
flame.
e. A chunk of iron takes months to rust completely while iron wool will rust in days.
____ 106. Which of the following statements about reaction orders in the rate law expression is incorrect?
a. Their values get larger as the temperature is increased.
b. Their values may or may not equal the stoichiometric coefficients in the balanced
equation.
c. An order equal to zero means there is no concentration dependence with rate.
d. Their values may equal the stoichiometric coefficients in the balanced equation.
e. Their values must be experimentally determined.
____ 107. Consider the following rate law expression: rate = k[A][B]2. If the concentration of A is tripled and the
concentration of B is reduced by half, what is the resulting change in the reaction rate?
a. The rate is reduced by 1/2.
b. The rate is increased by 3/2.
c. The rate is reduced by 3/4.
d. The rate is doubled.
e. The rate stays the same.
____ 108. Evaluate the specific rate constant for the reaction at the temperature for which the data were obtained. The
rate-law expression is rate = k[A][B]2.
A+BC
Experiment
1
2
3
a.
b.
c.
d.
e.
Initial [A]
0.10 M
0.20 M
0.10 M
Initial [B]
0.10 M
0.20 M
0.20 M
Initial Rate of Formation of C
4.0  104 M/min
3.2  103 M/min
1.6  103 M/min
3.6  102 M2min1
4.0  101 M2min1
6.2  101 M2min1
7.0  103 M2min1
1.2  102 M2min1
____ 109. Rate data have been determined at a particular temperature for the overall reaction
2NO + 2H2   + 2H2O
in which all reactants and products are gases.
Trial Run
1
2
3
Initial [NO]
0.10 M
0.10 M
0.20 M
Initial [H2]
0.20 M
0.30 M
0.20 M
Initial Rate (Ms1)
0.0150
0.0225
0.0600
What would be the initial rate of the reaction if the initial molar concentration of NO = 0.30 M and the initial
molar concentration of H2 = 0.10 M?
a. 0.068 Ms1
b. 0.22 Ms1
c. 0.040 Ms1
d. 0.10 Ms1
e. 0.022 Ms1
____ 110. The decomposition of dinitrogen pentoxide obeys the rate-law expression rate = 0.080 min1[N2O5]. If the
initial concentration of N2O5 is 0.30 M, what is the concentration after 2.6 minutes?
N2O5  N2O3 + O2
a.
b.
c.
d.
e.
0.32 M
0.13 M
0.24 M
0.028 M
0.38 M
____ 111. Cyclopropane rearranges to form propene in a reaction that is first order. If the rate constant is 2.74  103 s1,
how long would it take for 85.6% of the cyclopropane to rearrange if the initial concentration was 0.460 M?
a. 62.0 s
b. 707 s
c. 2.74  103 s
d. 3.83  104 s
e. 51.0 s
____ 112. Which statement is false?
a. If a reaction is thermodynamically spontaneous, it may occur rapidly.
b. A fast reaction may be thermodynamically spontaneous.
c. If a reaction is thermodynamically spontaneous, it may occur slowly.
d. Rate of reaction is a kinetic quantity rather than a thermodynamic quantity.
e. If a reaction is thermodynamically spontaneous, it must have a low activation energy.
____ 113. Reaction rates increase with increasing temperature because ____.
a. larger molecules collide more frequently
b. the activation energy increases
c. the energy of the transition state is lowered
d. the activation energy is decreased
e. a greater fraction of molecules possess the activation energy when they collide
____ 114. Which of the following statements regarding temperature and reaction rate is false.
a. The Arrhenius equation can be used to find the activation energy of a reaction.
b. The rate constant for a reaction decreases at lower temperatures.
c. A larger negative value of G0 causes a faster reaction rate.
d. Reaction rate always increases with higher temperature.
e. A larger value of Ea causes a slower reaction rate.
____ 115. The specific rate constant, k, for a reaction is 2.64  102 s1 at 25C, and the activation energy is 74.0 kJ/mol.
Calculate k at 50C. (The universal gas constant = 8.314 J/molK.)
a.
b.
c.
d.
e.
0.266 s1
1.08 s1
71.9 s1
0.832 s1
0.0265 s1
____ 116. The rate constant, k, for a first-order reaction is 1.20  102 s1 at 45C and the activation energy is 98.2
kJ/mol. Calculate the rate constant for this reaction at 95C.
a. 7.72  101 s1
b. 1.87  104 s1
c. 1.40  103 s1
d. 2.02  105 s1
e. 6.06  102 s1
____ 117. Calculate the activation energy of a reaction if its rate constant is 2.8  106 s1 at 24C and 1.5  107 s1 at
48C.
a. 67 J/mol
b. 55 kJ/mol
c. 26 kJ/mol
d. 80. kJ/mol
e. 3.51 J/mol
____ 118. What would be the activation energy of a reaction if its rate constant at 35C was double the value of its rate
constant at 25C?
a. 75.1 kJ/mol
b. 63.8 kJ/mol
c. 68.3 J/mol
d. 52.9 kJ/mol
e. 8.12 kJ/mol
____ 119. A catalyst ____.
a. changes the activation energy of the reaction
b. is always a solid
c. is used up in a chemical reaction
d. changes the value of G0 of the reaction
e. does not influence the reaction in any way
2 ICl + H2  I2 + 2 HCl
is first order in ICl and second order in H2. In an experiment to determine the rate law, the rate
constant was determined to be 2.24 M-2s-1. Using this value for the rate constant, the rate of the
reaction when [ICl] = 0.314M and [H2] = 0.179M would be:
a. 2.25 x 10-2 Ms-1
b. 2.52 x 10-1 Ms-1
c. 2.23 x 102 Ms-1
____ 120. The reaction of ICl with hydrogen :
d. 1.26 x 10-3 Ms-1
e. 3.95 x 10-2 Ms-1