Guide to Chapter 12. Chemical Kinetics
We will spend four lecture days on this chapter. During the first class meeting we will focus on what is kinetics
and how do we understand reaction rates, rate laws, rate constants, and similar vocabulary. Keeping the
vocabulary straight is critical. Next we will learn how to analyze experimental data of two types: initial
concentration/rates and then time/concentration studies. For both, we will use the following vocabulary:
reaction order, first, second and zeroth order reactions, and half-life. After we are comfortable with reaction
rate laws and how they are determined, we will then tie these mathematical expressions to step-by-step
chemical processes called the reaction mechanism. Finally, we will explore how catalysts work and how
temperature affects reaction rates.
Read the introductory paragraph to Chapter 12.
Read Section 12.1 Reaction Rates.
Learning Objective 1: Determine the rate of a chemical reaction given concentration (y) vs. time (x)
data. Use this data to determine the initial rate, average rate, and instantaneous rate. Hint: Review
how to determine the slope of a straight line plot.
Learning Objective 2: Know the units of reaction rate
Learning Objective 3: Given the reaction rate based on a certain reactant or product, determine the
relative reaction rate in terms of any other species in the reaction.
Do Problems 1 and 2 at the end of the section.
Do the following end-of-chapter problems: 30, 34, 36, 38
Problem Club Question A. Use seconds as the time component in the following three questions:
What are the units for rate?
What are the units for the rate constant in the expression rate = k[A]?
What are the units for the rate constant in the expression rate = k[A]2?
Problem Club Question B. For the reaction: O3 + NO 
→ O2 + NO2 at 310o K, the rate expression is:
rate = k[O3][NO] and k = 3.0 x 106 L mol-1 s-1. Given that [O3] = 2.0 x 10-6 M and [NO] = 1.4 x 10-6 M
at some point in the reaction, calculate the rate at that point - give units!
Problem Club Question C. For the reaction: 2 O3 
→ 3 O2, it was found that the rate of disappearance
-7
of O3 was 2.4 x 10 mol/L s. Calculate the rate of appearance of oxygen molecules, O2.
Read Section 12.2 Rate laws and reaction order
Learning Objective 4: Determine the reaction order from a given rate law.
Learning Objective 5: Given the rate law for a reaction, the rate constant and the reactant
concentration(s), calculate the rate of the reaction.
Learning Objective 6: Given the rate law for a reaction, the reaction rate and the reactant
concentrations, determine the rate constant, k.
Learning Objective 7: Determine the units for the rate constant, k.
Do Problem 3 at the end of Section 12.2.
Do the following end-of-chapter problems: 22, 40, 42, 44
Dr. Mattson, General Chemistry, Chm 205, Guide to Chapter 12. Chemical Kinetics
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Problem Club Question D. A reaction and its rate
expression are given below. When [C4H6] = 2.0 mol/L,
the rate is 0.106 mol/L s. What is the rate when [C4H6]
= 4.0 mol/L? Hint: Use the rate expression, the rate
(0.106 mol/L s) and the corresponding concentration (2.0
M) to solve for the rate constant. Next use the rate
constant and the new concentration, 4 M, to solve for the
new rate.
2 C 4 H6 
→ C8H12 rate = k[C4H6]2
Problem Club Question E. The oxidation of ammonia
produces nitrogen and water as shown below. If the rate
of formation of N2 is 0.70 M/s, determine the rates at
which NH3 and O2 are consumed.
4 NH3 + 3 O2

→
2 N2 + 6 H2O
Problem Club Question F. What is the reaction order for the
rate law: rate = k[A]2?
Problem Club Question G. The decomposition of NOCl is
second order in NOCl. When [NOCl]o = 0.30 M, the rate
is 3.60 x 10-9 M/s. Calculate k.
Problem Club Question H. (ACS-Style) The rate expression for a second order reaction is
(A)
(B)
rate = k [A]
rate = k [A] [B]
(C)
(D)
rate = k [A]2 [B]
rate == k [A]2 [B]2
Problem Club Question I. (ACS-Style) Some chemical reactions proceed at a rate that is proportional to the
concentration of a single reactant. Such reactions
(A) are called zero order reactions.
(B) are called first order reactions.
(C) are called second order reactions.
(D) do not occur. For a reaction to occur, at least two molecules (or ions) must collide; in this case,
however, there is only one reactant.
Problem Club Question J. (ACS-Style) The rate law for the reaction
A+B→C+D
is first order in [A] and second order in [B]. If [A] is halved and [B] is doubled, the rate of the reaction
will
(A) remain the same.
(B) be increased by a factor of 2.
(C) be increased by a factor of 4.
(D) be increased by a factor of 8.
Read Section 12.3 Experimental determination of a rate law.
Learning Objective 8: Given initial rate/initial concentration data
a. Write the rate law for a given reaction.
b. Determine the order with respect to each reactant.
c. Determine the overall reaction order.
d. Calculate the rate constant, k, (using proper units).
e. Determine the rate of reaction given the concentration of the reactant(s).
Do Problems 4 - 6 at the end of the section.
Do the following end-of-chapter problems: 46, 48
Dr. Mattson, General Chemistry, Chm 205, Guide to Chapter 12. Chemical Kinetics
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Problem Club Question K. Consider the following data for the reaction of A
the rate expression using the Initial Concentration Initial Rate Method
Initial [A]
Initial Rate, Δ[P]/ Δt
1.0
0.012 mol/L hr
2.0
0.024
3.0
0.035

→
P in order to determine
Problem Club Question L. Consider the following data for the reaction A + B 
→ P in order to
determine the rate expression using the Initial Concentration Initial Rate Method
Initial [A]
Initial [B]
Initial Rate
1.0
1.0
0.012
2.0
1.0
0.024
3.0
1.0
0.035
2.0
2.0
0.096
1.0
2.0
0.048
Problem Club Question M. Consider the reaction: 2 NO + 2 H2
in order to determine the rate expression for the reaction.
Expt
Initial [NO]
Initial [H2]
1
1.00
1.00
2
1.20
1.20
3
0.80
0.80
4
1.00
2.00
5
2.00
1.00

→
N2 + 2 H2O and the following data
Initial Rate (mol/L s)
3.5 x 10-5
5.0 x 10-5
1.8 x 10-5
7.0 x 10-5
1.4 x 10-4
Problem Club Question N. (ACS-Style) Initial rate data for the reaction follows.
2N2O5(g) 
→ 4NO2(g) + O2(g)
Experiment
[N2O5]
[O2]Rate in M·s–1
1
0.15 M
0.30 M
46
2
0.20 M
0.60 M
61
3
0.20 M
0.30 M
61
€
What is the rate law for this reaction?
(A)
rate = k[N2O5] (C)
rate = k[N2O5]1.3[O2]2
(B)
€
rate = k[[N2O5]2 (D)
rate = k[N2O5]2[O2]
Problem Club Question O. (ACS-Style) For the reaction A + B → C these data were obtained:
Initial
Initial
Initial Rate of
Expt.
Conc. A
Conc. B
formation of C
I
0.10 M
0.10 M
0.030 M·h–1
II
0.10 M
0.20 M
0.12 M·h–1
III
0.20 M
0.20 M
0.12 M·h–1
The rate law for this reaction is
(A)
rate = k [A] [B]
(C)
rate = k [A]2 [B]
2
(B)
rate = k [A]
(D)
rate = k [B]2
Problem Club Question P. (ACS-Style) For the reaction between gaseous chlorine and nitric oxide:
2NO(g) + Cl2(g) → 2NOCl(g)
doubling the concentration of chlorine doubles the rate of reaction. Doubling the concentrations of both
reactants increases the rate by a factor of eight. The reaction is
(A)
first order in NO, first order in Cl2.
(B)
first order in NO, second order in Cl2.
(C)
second order in NO, second order in Cl2.
(D)
second order in NO, first order in Cl2.
Dr. Mattson, General Chemistry, Chm 205, Guide to Chapter 12. Chemical Kinetics
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Read Sections 12.4 - 12.7. These four sections are perhaps the most important sections
in the chapter in terms of evaluating experimental data to determine the rate law.
They are combined here because they will be presented all together in lecture.
Individual section titles: Section 12.4. Integrated rate law for a first order reaction;
Section 12.5. Half-life of a first-order reaction; Section 12.6. Second-order reactions;
and Section 12.7. Zeroth-order reactions.
Learning Objective 9: Use concentration(y) vs. time(x) data to determine the reaction order (zero, first,
or second) with respect to a single reactant
Learning Objective 10: After establishing the rate law (previous objective), determine the value of the
rate constant, k (with proper units)
Learning Objective 11: Having established the rate law, and given the concentration of the reagent,
determine the reaction rate.
Learning Objective 12: Using the integrated rate law equations (handout) and knowing the reaction
order determine the following values:
a. rate constant, k
b. reaction time for a given percent completion of a reaction.
c. the concentration of a reactant after a given period of time.
d. The time it takes for a given change in the concentration of the reactant.
e. half-life
Learning Objective 13: Given graphical representations of concentration vs. time, select the graph that
corresponds to the correct reaction order.
Do Problems 7 - 11 embedded within these sections.
Do the following end-of-chapter problems: 24, 26, 50, 52, 54, 56, 58, 60, 62, 64
Problem Club Question Q. The reaction CCl3CO2H(aq)
70oC according to the following data:

→
CO2 + CHCl3 was found to proceed at
time, h [CCl3CO2H];
0.00
0.1000
1.00
0.0940
2.00
0.0884
3.00
0.0831
4.00
0.0782
a. Determine the order of the reaction
b. Determine the value of the rate constant
c. Determine the concentration of CCl3CO2 after 5.00 hours and 10.00 hours
d. How long would it take for the concentration of CCl3CO2H to drop from 0.10000 mol/L down to
0.09000 mol/L?
e. How long would it take for the reaction to become 95% complete? Hint: Make the final concentration
equal to 5% of the initial concentration because 95% of it is gone.
Problem Club Question R. The reaction: A 
→ products was found to proceed according to the data
that follows.
t, min [CCl3CO2H]
0.00
0.1000
1.00
0.0900
2.00
0.0800
3.00
0.0700
a. What is the rate expression and the order of the reaction?
b. Determine the value of the rate constant
c. What is the half life?
d. Determine the concentration of A after 2.40 minutes and 5.00 minutes.
e. How long would it take for the concentration of A to drop from 0.10000 mol/L down to 0.02000
mol/L?
f. How long would it take for the reaction to become 98% complete?
Dr. Mattson, General Chemistry, Chm 205, Guide to Chapter 12. Chemical Kinetics
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Problem Club Question S. At 25oC, the reaction I- + ClO- 
→ IO- + Cl- proceeds according to the rate
law: rate = k[I-]2 where k = 0.0606 L mol-1s-1. If a solution is initially 0.00350 M with respect to each
reactant, what will be the concentration of each species present after 300 s? Hint: Use the time-conc
equation for the appropriate order - also note that the rate only depends on the concentration of iodide.
Problem Club Question T. What is the half life for a first order reaction if the rate constant, k = 2.05 x 10-2
s-1?
Problem Club Question U. Rate constants for several first order reactions are: 0.0410 s-1, 0.521 s-1, 0.0033
s-1, 1.83 s-1, and 2.00 s-1. The half life is shortest for the reaction with which k value?
Problem Club Question V. At 500oC, the decomposition of XY4(g) to its elements yields these data below.
What is the concentration of XY4 after 5 hours? Hint: Determine the rate expression first, then determine
k, finally solve for the concentration after 5 hrs.
Time
[XY4]
0 hr
2.11
1 hr
1.79
2 hr
1.47
3 hr
1.15
Problem Club Question W. A reaction that is first order has a rate constant of 4.5 min-1. How long will it
take for the concentration of reactant to change from 0.40 M to 0.05 M?
Problem Club Question X. A second order reaction has an initial concentration of reactant equal to 0.02 M.
If the rate constant is 10 M-1s-1, calculate the time required to decrease the concentration to 0.005 M.
Problem Club Question Y. (ACS-Style) For the following reaction, which plot confirms that the rate is first
order with respect to H2O2?
2H2O2 → 2H2O + O2
(A)
(B)
(C)
(D)
Problem Club Question Z. (ACS-Style) Substance A undergoes a first order reaction A → B with a half life
of 20 min at 25 °C. If the initial concentration of A in a sample is 1.6 M, what will be the concentration
of A after 80 min?
(A)
0.40 M (B)
0.20 M (C)
0.10 M (D)
0.050 M
Read Sections 12.8 Reaction Mechanisms and Section 12.9. Rate laws and reaction
mechanisms
Learning Objective 14: Write the overall reaction from a given mechanism.
Learning Objective 15: Determine the "molecularity" of an elementary step in a given mechanism.
Learning Objective 16: Write the rate law for any elementary step in a given reaction mechanism.
Dr. Mattson, General Chemistry, Chm 205, Guide to Chapter 12. Chemical Kinetics
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Learning Objective 17: Given a reaction
mechanism with two or more steps, identify the
intermediate(s), if present.
Learning Objective 18: Derive the rate law from
a given reaction mechanism.
Learning Objective 19: Determine which of
several proposed mechanisms is consistent with
a given rate law.
Do Problems 12 - 14 embedded within these
sections.
Do the following end-of-chapter problems: 66, 68,
70, 72, 74, 76
Problem Club Question BB. The reaction of CO2
with hydroxide ion in aqueous solution is
postulated to occur according to the mechanism
below. What is the rate law for the mechanism?
CO2(aq) + OH-(aq) 
slow
→ HCO3-(aq)
2HCO3 (aq) + OH (aq) 
fast
→ CO3 (aq) + H2O
Problem Club Question CC. The available kinetic data for the reaction 2 NO(g) + O2(g) 
→ 2 NO2(g) is
consistent with the following reaction mechanism. Obtain the rate law for the reaction from the proposed
mechanism. What is the role of NO3?
NO(g) + O2(g)
NO3(g)
fast
NO(g) + NO3(g) 
→ 2 NO2(g) slow
Problem Club Question DD. (ACS-Style) Consider the reaction: 2NO2(g) + F2(g)
proposed mechanism for this reaction is
NO2 + F2 
(slow)
→ NO2F + F
NO2 + F
What is the rate law for this mechanism?
[NO2F]2
(A)
rate = k
(C)
[NO2]2[F2]
(B)
rate = k [NO2]2 [F2]
(D)
NO2F
2NO2F(g). A
(fast)
rate = k [NO2] [F2]
rate = k [NO2] [F]
Problem Club Question EE. (ACS-Style) For the following reaction, the mechanism was determined to be
X2 + Y + Z → XY + XZ
Mechanism:
l)
X2 + Y → XY + X (very slow)
2)
X + Z → XZ
(very fast)
What is the rate law for this reaction?
(A)
rate = k [X2] [Y] [Z]
(C)
rate = k [X] [Z]
(B)
rate = k [X2]
(D)
rate = k [X2] [Y]
€
Dr. Mattson, General Chemistry, Chm 205, Guide to Chapter 12. Chemical Kinetics
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Problem Club Question FF. (ACS-Style) The reaction 2A + 2B → C + D proceeds by this mechanism:
→
2A ←
A2
(equilibrium)
A2 + B → X + C (rate determining)
X+B→D
(rapid)
The rate equation for the reaction is
[Al2 [B]2
(A) rate = k[A] [B]
(C)
rate = k
[C] [D]
(B) rate = k[A]2 [B]2 (D)
rate = k[A]2 [B]
Read Section 12.10 and 12.11 on reaction rates and temperatures.
Learning Objective 20: List the factors that are important for a reaction going to completion according
to the collision model.
Learning Objective 21: Interpret and identify the different parts of a potential energy profile diagram.
Determine if the diagram is for an exothermic or endothermic reaction. The areas on the diagram to
identify include: the reactant energy, product energy, the transition state, the energy of activation
(forward), the energy of activation (reverse), and ΔH.
Learning Objective 22: Given known energies in an energy profile diagram, determine the missing
energy.
Learning Objective 23: Describe how increasing the temperature can effect the rate of a chemical
reaction.
Learning Objective 24: Use the Arrhenius equation to determine the energy of activation, Ea, for a
reaction.
Do Problems 15 and 16 embedded within these sections.
Do the following end-of-chapter problems: 28, 78, 80, 82, 84, 86
Problem Club Question GG. For the given reaction rate law: rate = k[A][B]2, which of the following will
change the value of the rate constant, k?
A. doubling [A]
D. decreasing the temperature
B. doubling [B]
E. more than one of the above.
C. removing some product
Problem Club Question HH. A certain reaction has Ea = 146 kJ/mol. If the specific rate constant is 4.25 x
10-4 s-1 at 25oC, what is the rate constant at 100oC?
Problem Club Question II. For a certain reaction, the activation energy is 62 kJ and the enthalpy change is
-22 kJ. Sketch this energy profile and label both forward and reverse activation energies. What is Eact
for the reverse reaction?
Problem Club Question JJ. (ACS-Style) The decomposition of hydrogen peroxide in the presence of iodide
ion is believed to occur via the mechanism
H2O2(aq) + I–(aq) → H2O(l) + IO–(aq)
H2O2(aq) + IO–(aq) → H2O(l) + O2(g) + I–(aq)
In this mechanism, I–(aq) is
(A)
(B)
(C)
(D)
a catalyst.
a reactant in the overall reaction.
the activated complex.
a product of the overall reaction.
Dr. Mattson, General Chemistry, Chm 205, Guide to Chapter 12. Chemical Kinetics
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Problem Club Question KK. (ACS-Style) A change in temperature from 10 °C to 20 °C is found to double
the rate of a given chemical reaction. How did this change affect the reacting molecules?
(A) It doubled their average velocity.
(B) It doubled their average energy.
(C) It doubled the number of collisions per second.
(D) It doubled the pressure inside the reaction vessel.
(E) It doubled the proportion of molecules possessing at least the minimum energy required for the
reaction.
Problem Club Question LL. (ACS-Style) The value of the rate constant of a reaction can generally be
expected to
(A) be independent of temperature.
(B) increase with increasing temperature.
(C) decrease with increasing temperature.
(D) decrease with increasing temperature only if the reaction is exothermic.
Read Section 12.12. Catalysis and Section 12.13. Homogeneous and heterogeneous
catalysts.
Learning Objective 25: Describe the role of a catalyst and explain the difference between a homogeneous
and a heterogeneous catalyst. Know how a catalyst affects a potential energy profile diagram.
Learning Objective 26: Given a reaction mechanism, identify the following: the catalyst (if present), the
intermediate(s) (if present), and the rate-determining step.
Do Problem 17 embedded within these sections.
Do the following end-of-chapter problems: 88, 90, 92, 94
Problem Club Question MM. A catalyst:
A. decreases the activation energy.
B. changes ΔH for the reaction.
C. is chemically changed by the reaction
D. changes the rate determining step
E. decreases the value of the rate constant
Problem Club Question NN. (ACS-Style) A catalyst will
(A) alter the pathway (mechanism) of a chemical reaction.
(B) increase ΔH for the reaction.
(C) decrease ΔH for the reaction.
(D) decrease Ea for the forward reaction only.
Problem Club Question OO. (ACS-Style) The addition of a catalyst in a chemical reaction
(A) increases the concentration of products at equilibrium.
(B) increases the fraction of reactant molecules with a given kinetic energy.
(C) provides an alternate path with a different activation energy.
(D) lowers the enthalpy change in the overall reaction.
Dr. Mattson, General Chemistry, Chm 205, Guide to Chapter 12. Chemical Kinetics
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Answers
A. a. moles L-1 s-1
b. s-1
c. L mol-1 s-1
B. rate = 8.4 x 10-6 mol L-1 s-1
C. 3.6 x 10-7 mol L-1 s-1
D. 0.424 mol/L s
E. Δ [NH3] / Δt = 1.4 mol/L s; Δ[O2] / Δt = 1.05 mol/L s
F. second
G. 4.0 x 10-8 L/mol s
H. B
I. B
J. B
O. D
P. D
K. rate = k[A]
L. rate = k[A][B]2
M. rate = k[NO]2[H2]
N. A
Q. 4.
a. first
d. 1.71 h
b. k = 0.0615 h-1
e 48.7 h
R. a. rate = k; zero b. k = 0.01 mol L-1 min-1
min: 0.050 mol/L
e. 8 min
c. 5 h: 0.0735 mol/L and 10 h: 0.0540 mol/L
c. 5 min
f. 9.8 min
d. 2.4 min: 0.076 mol/L
5.0
S. both will be 0.00329 M
T. 33.8 s
U. 2.00 s-1
V. 0.51 M
W. 0.46 min
X. 15 s
Y. D
Z. C
BB. rate = k [CO2][OH-]
CC. rate = k [NO]2[O2]; NO3 is intermediate
DD. C
EE. D
FF. D
GG. D
KK. E
LL. B
MM. A
HH. 59 s-1
II. 84 kJ
JJ. A
NN. A
Dr. Mattson, General Chemistry, Chm 205, Guide to Chapter 12. Chemical Kinetics
OO. C
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