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• Chapter 12Chemical Kinetics

Consider the reaction 2H2 + O2 ( 2H2O. What is the ratio of the initial rate of the appearance of water to the initial rate of disappearance of oxygen?

1)1 : 1

2)2 : 1

3)1 : 2

4)2 : 2

5)3 : 2

Consider the reaction X ( Y + Z. Which of the following is a possible rate law?

1)Rate = k[X]

2)Rate = k[Y]

3)Rate = k[Y][Z]

4)Rate = k[X][Y]

5)Rate = k[Z]

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]0Initial Rate

1 ( 10181 ( 10182.0 ( 1016

2 ( 10181 ( 10188.0 ( 1016

3 ( 10181 ( 101818.0 ( 1016

1 ( 10182 ( 10184.0 ( 1016

1 ( 10183 ( 10186.0 ( 1016

Which of the following is the correct rate law?

1)Rate = k[NO][O2]

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

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

4)Rate = k[NO]2

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

A general reaction written as 1A + 2B ( C + 2D is studied and yields the following data:

[A]0[B]0Initial ([C]/(t

0.150 M0.150 M8.00 ( 103 mol/L ( s

0.150 M0.300 M1.60 ( 102 mol/L ( s

0.300 M0.150 M3.20 ( 102 mol/L ( s

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

1)0

2)1

3)2

4)3

5)4

Consider the following data concerning the equation: H2O2 + 3I + 2H+ ( I3 + 2H2O

[H2O2][I][H+]rate

a.0.100 M5.00 ( 104 M1.00 ( 102 M0.137 M/sec

b.0.100 M1.00 ( 103 M1.00 ( 102 M0.268 M/sec

c.0.200 M1.00 ( 103 M1.00 ( 102 M0.542 M/sec

d.0.400 M1.00 ( 103 M2.00 ( 102 M1.084 M/sec

Two mechanisms are proposed:

a.H2O2 + I ( H2O + OI

OI + H+ ( HOI

HOI + I + H+ ( I2 + H2O

I2 + I ( I3

b.H2O2 + I + H+ ( H2O + HOI

HOI + I + H+ ( I2 + H2O

I2 + I ( I3

Which of the following describes a potentially correct mechanism?

1)Mechanism a with the first step the rate determining step.

2)Mechanism a with the second step the rate determining step.

3)Mechanism b with the first step rate determining.

4)Mechanism b with the second step rate determining.

5)None of these could be correct.

For the reaction 2N2O5(g) ( 4NO2(g) + O2(g), the following data were collected:

t (minutes)[N2O5] (mol/L)

01.24 ( 102

10.0.92 ( 102

20.0.68 ( 102

30.0.50 ( 102

40.0.37 ( 102

50.0.28 ( 102

70.0.15 ( 102

The half-life of this reaction is approximately:

1)15 minutes.

2)18 minutes.

3)23 minutes.

4)36 minutes.

5)45 minutes.

Determine the molecularity of the following elementary reaction: O3 ( O2 + O.

1)Unimolecular

2)Bimolecular

3)Termolecular

5)The molecularity cannot be determined.

The decomposition of ozone may occur through the two-step mechanism shown:

step 1O3 ( O2 + O

step 2O3 + O ( 2O2

The oxygen atom is considered to be a(n):

1)reactant.

2)product.

3)catalyst.

4)reaction intermediate.

5)activated complex.

Under certain conditions the reaction H2O2 + 3I + 2H+ ( I3 + 2H2O occurs by the following series of steps:

Step 1.H2O2 + H+

H3O2+

EQ \B\BC\((rapid equilibrium constant K = \F(k1,k1))

Step 2.H3O2+ + I ( H2O + HOI (slow, rate constant k2)

_1149790915.unknown

_1150826653.doc

_1149173435.bin

Step 3.HOI + I ( OH + I2 (fast, rate constant k3)

Step 4.OH + H+ ( H2O (fast, rate constant k4)

Step 5.I2 + I ( I3 (fast, rate constant k5)

_1149173435.bin

Which of the steps would be called the rate-determining step?

1)1

2)2

3)3

4)4

5)5

_1149173435.bin

Under certain conditions the reaction H2O2 + 3I + 2H+ ( I3 + 2H2O occurs by the following series of steps:

Step 1.H2O2 + H+

H3O2+

EQ \B\BC\((rapid equilibrium constant K = \F(k1,k1))

Step 2.H3O2+ + I ( H2O + HOI (slow, rate constant k2)

_1149790915.unknown

_1150826653.doc

_1149173435.bin

Step 3.HOI + I ( OH + I2 (fast, rate constant k3)

Step 4.OH + H+ ( H2O (fast, rate constant k4)

Step 5.I2 + I ( I3 (fast, rate constant k5)

_1149173435.bin

The rate constant k for the reaction would be given by:

1)k = k2

2)k = k2k3

3)k = k2K

4)k = k5

5)k = Kk2k3k4k5

_1149173435.bin

Refer to the following diagram:

Why is this reaction considered to be exothermic?

1)Because energy difference B is greater than energy difference C

2)Because energy difference B is greater than energy difference A

3)Because energy difference A is greater than energy difference C

4)Because energy difference B is greater than energy difference C plus energy difference A

5)Because energy difference A and energy difference C are about equal

Refer to the following diagram:

At what point on the graph is the activated complex present?

1)Point W

2)Point X

3)Point Y

4)Point Z

5)None of these

Refer to the following diagram:

If the reaction were reversible, would the forward or the reverse reaction have a higher activation energy?

1)The diagram shows no indication of any activation energy.

2)The forward and reverse activation energies are equal.

3)The forward activation energy

4)The reverse activation energy

5)None of these

Which of the following statements is typically true for a catalyst?

1)The concentration of the catalyst will go down as a reaction proceeds.

2)The catalyst provides a new pathway in the reaction mechanism.

3)The catalyst speeds up the reaction.

4)Two of these

5)None of these

• Copyright Houghton Mifflin Company. All rights reserved.CRS Question, 12*ANSWER4) Two of these Section 12.8 Catalysis (p. 557) The catalyst provides a new pathway in the reaction mechanism and the catalyst speeds up the reaction.

The catalyzed pathway in a reaction mechanism has a(n) __________ activation energy and thus causes a(n) __________ reaction rate.

1)higher; lower

2)higher; higher

3)lower; higher

*HMCLASS PRESENT: Video: Reaction Rates and Concentration

*HMCLASS PRESENT: Animation: Decomposition of N2O5HMCLASS PRESENT: Video: An Oscillating Reaction

*STUDENT CD: Understanding Concepts: Transition States and Activation Energy

*HMCLASS PRESENT: Video: Catalysis

*HMCLASS PRESENT: Animation: Heterogeneous Catalysis