Name____________________________________________
Block
Kinetics
Info
Problems from the following texts:
Chemistry by Brown, LeMay, Bursten
Chemistry by Moore, Stanitski, Jurs
Homework
TEST REVIEW (Answer as you learn them? Wait till the end? This might get assigned….)
1. What are orders? What does it mean to have an order with respect to a reactant? How do you find overall orders?
How could you use experimental data to calculate orders?
2. How will making changes to a system change the rate? Temperature? Concentrations?
3. Be able to use experimental data to solve for rate laws and rate constants.
4. What is activation energy? What other things affect whether a reaction will take place? What is a frequency factor?
𝐸𝑎 1
Understand how to use the equation: ln(𝑘) = − 𝑅 (𝑇) + 𝑙𝑛(𝐴)
5. What factors affect rates specifically? (discuss in relation to energy / rxn coordinate graph)
6. You are given initial rates and initial concentrations. What do you do? How do you do it? How do you solve for k?
How do you figure out the units of k?
7. You are given time and concentration. What do you do? How do you do it? How do you solve for k? How do you
figure out the units of k?
8. You are given temperatures and rate constants. What do you do? How do you get Kelvin? What equation will you
work with? What is A? What are its units? What is Ea? What are its units? What value of R should you use?
9. What are reaction mechanisms? What is a rate-determining step? What is an elementary reaction? What is an
intermediate? How do you determine the rate law if you’re given a reaction mechanism? How do you select a
reaction mechanism if you’re given an experimentally determined rate law?
10. Complete the following problem from an old AP test:
For a hypothetical chemical reaction that has the stoichiometry 2 X + Y  Z, the following initial rate data were
obtained. All measurements were made at the same temperature.
Initial Rate of
Formation of Z,
(a)
Give the rate law for this reaction from the data above.
Initial [X]o,
Initial [Y]o,
(mol.L-1.sec-1)
(mol.L-1)
(mol.L-1)
(b)
Calculate the specific rate constant for this reaction and specify
its units.
0.20
0.10
7.010-4
(c)
How long must the reaction proceed to produce a concentration
of
Z
equal
to 0.20 molar, if the initial reaction concentrations are [X] o =
0.40
0.20
1.410-3
0.80 molar, [Y]o = 0.60 molar and [Z]0 = 0 molar?
(d)
Select from the mechanisms below the one most consistent with
-3
0.40
0.40
2.810
the observed data, and explain your choice. In these mechanisms M and
N are reaction intermediates.
0.60
0.60
4.210-3
(1) X + Y  M (slow)
X + M  Z (fast)
(2) X + X  M (fast)
Y + M  Z (slow)
1
(3) Y  M
(slow)
M + X  N (fast)
N + X  Z (fast)
Reaction Mechanisms
H2(g) + ICl(g)  HI(g) + HCl(g)
HI(g) + ICl(g)  I2(g) + HCl(g)
(a) Write the balanced equation for the overall
reaction. (b) Identify any intermediates in the
mechanism. (c) Write rate laws for each
elementary reaction in the mechanism. (d) If the
first step is slow and the second one is fast, what
rate law do you expect to be observed for the
overall reaction?
7. The decomposition of hydrogen peroxide is
catalyzed by iodide ion. The catalyzed reaction is
thought to proceed by a two-step mechanism:
H2O2(aq) + I-(aq)  H2O(l) + IO-(aq)
(slow)
IO (aq) + H2O2(aq)  H2O(l) + O2(g) + I (aq) (fast)
(a) Write rate laws for each elementary reaction
in the mechanism. (b) Write the chemical
equation for the overall process. (c) Identify the
intermediates, if any, in the mechanism. (d)
Assuming the first step of the mechanism is rate
determining, predict the rate law for the overall
process?
8. The reaction 2NO(g) + Cl2(g)  2NOCl(g) obeys
the rate law, rate = k[NO]2[Cl2]. The following
mechanism has been proposed for this reaction:
NO(g) + Cl2(g)  NOCl2(g)
NOCl2(g) + NO(g)  2NOCl(g)
(a) What would the rate law be if the first step
were rate determining? (b) Based on the
observed rate law, what can we conclude about
the relative rates of the two steps?
9. You have studied the gas-phase oxidation of HBr
by O2:
4HBr(g) + O2(g)  2H2O(g) + 2Br2(g)
You find the reaction to be first order with
respect to HBr and first order with respect to O2.
You propose the following mechanism:
HBr(g) + O2(g)  HOOBr(g)
HOOBr(g) + HBr(g)  2 HOBr(g)
HOBr(g) + HBr(g)  H2O(g) + Br2(g)
(a) Indicate how the elementary reactions add to
give the overall reaction.
(Hint: You will
need to multiply the coefficients of one of the
equations by 2.) (b) Based on the rate law, which
step is rate determining? (c) What are the
1. (a) What is meant by the term elementary
reaction? (b) What is the difference between a
unimolecular and a bimolecular elementary
reaction? (c) What is a reaction mechanism?
2. (a) What is meant by the term molecularity? (b)
Why are termolecular elementary reactions so
rare? (c) What is an intermediate in a
mechanism?
3. What is the molecularity of each of the following
elementary reactions? Write the rate law for
each.
a. Cl2(g)  2Cl(g)
b. OCl-(aq) + H2O(l)  HOCl(aq) + OH-(aq)
c. NO(g) + Cl2(g)  NOCl2(g)
d. 2 NO(g)  N2O2(g)
e. SO3(g)  SO2(g) + O2(g)
4. Based on the following reaction profile, how
many intermediates are formed in the reaction A
 D? (b) How many transition sates are there?
(c) Which step is the fastest? (d) Is the reaction A
 D exothermic or endothermic?
5. Consider the following energy profile.
(a) How many elementary reactions are in the
reaction mechanism? (b) How many
intermediates are formed in the reaction? (c)
Which step is rate limiting? (d) Is the overall
reaction exothermic of endothermic?
6. The following mechanism has been proposed for
the gas-phase reaction of H2 with ICl:
2
intermediates in this mechanism? (d) If you are
unable to detect HOBr or HOOBr among the
products, does this disprove your mechanism?
a.
What is the rate-law expression for this
reaction?
b. Describe the order of the reaction with respect
to each reactant and to the overall order.
10. When the rate of the reaction 2NO(g) + O2(g) 
2NO2(g) was studied, it was found that the rate
doubled when the O2 concentration alone was
doubled, but quadrupled when the NO
concentration alone was doubled. Which of the
following mechanisms accounts for these
observations?
(a) Step 1. NO + O2  NO3, and its reverse (both fast)
Step 2. NO + NO3  NO2 + NO2 (slow)
13. The reaction: (C2H5)2(NH)2 + I2  (C2H5)2N2 + HI
gives the following initial rates.
Expt. [(C2H5)2(NH)2]0
(mol/L)
(b) Step 1. NO + NO  N2O2 (slow)
Step 2. O2 + N2O2  N2O4 (fast)
Step 3. N2O4  NO2 + NO2 (fast)
Initial Rate of
Formation of
(C2H5)2N2
1
0.015
0.015
3.15 M • s-1
2
0.015
0.045
9.45 M • s-1
3
0.030
0.030
12.6 M • s-1
Write the rate-law expression and solve for the
constant.
Method of Initial Rates
14. The reaction: 2NO(g) + Cl2(g)  2NOCl(g)
was studied at -10°C. The following results were
obtained
[NO]0 (mol/L) [Cl2]0 (mol/L) Initial Rate
(mol/L •s)
0.10
0.10
0.18
0.10
0.20
0.36
0.20
0.20
1.45
a. What is the rate law?
b. What is the value of the rate constant?
11. Rate data were collected for the following
reaction at a particular temperature.
A+B
Products
Expt. Initial [A]
Initial [B]
Initial Rate of
(mol/L)
(mol/L)
Rxn (M•S-1)
1
0.10
0.10
0.0090
2
0.20
0.10
0.036
3
0.10
0.20
0.018
4
0.10
0.30
0.027
a. What is the rate-law expression for this
reaction?
b. Describe the order of the reaction with respect
to each reactant and to the overall order.
15. The reaction:
2I-(aq) + S2O82-(aq)  I2(aq) + 2SO42-(aq)
[I-]0 (mol/L)
2ClO2 (aq) + 2OH- (aq)ClO3- (aq) +ClO2- (aq) +H2O (l)
Initial [OH] (mol/L)
0.012
0.012
0.024
0.024
[S2O82-]0 (mol/L)
Initial Rate
(mol/L • s)
12.5 × 10-6
6.25 × 10-6
6.25 × 10-6
5.00 × 10-6
7.00 × 10-6
0.080
0.040
0.040
0.040
0.080
0.020
0.032
0.040
0.060
0.030
a. Determine the rate law.
b. Calculate a value for the rate constant for each
experiment and an average value for the rate
constant.
12. Rate data were collected for the following
reaction at a particular temperature.
Expt. Initial [ClO2]
(mol/L)
1
0.012
2
0.024
3
0.012
4
0.024
[I2]0
(mol/L)
Initial Rate of
Rxn (M•S-1)
2.07 x 10-4
8.28 x 10-4
4.14 x 10-4
1.66 x 10-3
3
16. Given these data for the reaction A + B  C,
write the rate-law expression and solve for the
constant.
Expt. Initial [A]
(M)
Initial [B]
(M)
1
2
3
0.10
0.10
0.20
0.20
0.30
0.40
[ClO2]0 (mol/L)
Initial Rate
(mol/L • s)
0.0033
0.0750
5.75 × 10-2
0.1000
0.1000
2.30 × 10-1
0.1000
0.0500
1.15 × 10-1
a. Determine the rate law and the value of the rate
constant.
b. What would be the initial rate for an experiment
with [ClO2]0 = 0.175 mol/L and [OH-]0 = 0.0844
mol/L?
Initial Rate of
Formation of C
(M • s-1)
5.0 × 10-6
7.5 × 10-6
4.0 × 10-5
17. Given these data for the reaction A + B  C,
write the rate-law expression and solve for the
constant.
Expt. Initial [A]
(M)
Initial [B]
(M)
1
2
3
0.15
0.30
0.60
0.25
0.25
0.50
20. The following data was collected for the rate of
disappearance of NO in the reaction
2NO(g) + O2(g) 2NO2 (g):
Initial Rate of
Formation of C
(M • s-1)
8.0 × 10-5
3.2 × 10-4
5.12 × 10-3
Expt
[NO]
[O2]
Initial Rate
.
Expt.
(M)
(M)
(M/s)
1
0.0126 0.0119 1.41 x10-2
2
0.0252 0.0250 1.13 x10-1
3
0.0252 0.0125 5.64 x10-2
a. What is the rate law for the reaction?
b. What are the units of the rate constant?
What is the average value of the rate constant
calculated from the three data sets?
18. The rate of the reaction between hemoglobin
(Hb) and carbon monoxide (CO) was studied at
20°C. The following data were collected with all
concentration unites in µmol/L. (A hemoglobin
concentration of 2.21 µmol/L is equal to 2.21 ×
10-6 mol/L.)
[Hb]0 (µmol/L)
[OH-]0 (mol/L)
21. Consider the gas-phase reaction between nitric
oxide and bromine at 273°C: 2NO (g) + Br2 (g)
2NOBr (g). The following data for the initial
rate of appearance of NOBr were obtained:
[CO]0 (µmol/L)
Initial Rate
(µmol/L • s)
2.21
1.00
0.619
2.21
2.00
1.24
4.42
4.00
4.95
a. Determine the orders of this reaction with
respect to Hb and CO.
b. Determine the rate law.
c. Calculate the value of the rate constant.
d. What would be the initial rate for an experiment
with [Hb]0 = 3.36 µmol/L and [CO]0 = 2.40
µmol/L?
Expt
[NO] (M)
[Br2] (M)
1
2
3
4
0.10
0.25
0.10
0.35
0.20
0.20
0.50
0.50
Initial Rate
(M/s)
24
150
60
735
a. Determine the rate law.
b. Calculate the average value of the rate constant
for the appearance of NOBr from the four data
sets.
c. How is the rate of appearance of NOBr related to
the rate of disappearance of BR2?
d. What is the rate of disappearance of Br2 when
[NO] = .075M and [Br2] = .185M
19. The following data were obtained for the
reaction
2ClO2(aq) + 2OH-(aq)ClO3-(aq) + ClO2-(aq) + H2O(l)
4
22. The following kinetic data were obtained for the
reaction 2ICl (g) + H2 (g) I2 (g) + 2 HCl (g):
Expt
[ICl]0 (M)
[H2]0 (M)
1
2
3
4
1.5
3.0
3.0
4.7
1.5
1.5
4.5
2.7
Integrated Rate Law
Initial Rate
(mmol/L•s)
0.37
0.74
2.2
?
26. For the reaction Aproducts. Successive halflives are observed to be 10.0, 20.0, and 40.0 min
for an experiment in which [A]0 = 0.10 M.
Calculate the concentration of A at the following
times given the orders.
a. 80.0 min if the reaction is first order
b. 30.0 min if the reaction is second order
a. Write the rate law for the reaction.
b. From the data, determine the value of the rate
constant.
c. Use the data to predict the initial rate for
experiment 4.
27. The reaction
NO(g) + O3(g)  NO2(g) + O2(g)
was studied by performing two experiments. In the
first experiment the rate of disappearance of NO
was followed by the presence of a large excess of O3.
The results were as follows ([O3] remains effectively
constant at 1.0 x 1010 molecules/cm3):
Time (ms)
[NO] (molecules/cm3)
0
6.0 x 108
100 ± 1
5.0 x 108
Half-Life
*For first-order reactions ONLY, half-life is
independent of starting concentration. For all other
reaction orders, the half-life will depend on the
starting concentration.
*Be able to estimate half-lives of first-order
reactions from graphs
500 ± 1
2.4 x 108
700 ± 1
1000 ± 1
1.7 x 108
9.9 x 107
If the reaction is known to be second order with
respect to ozone, write the rate law expression for
the reaction.
23. The half-life of a certain first-order reaction is 15
minutes. What fraction of the original reactant
concentration will remain after 2.0 hours?
28. The thermal decomposition of ammonia at high
temperatures was studied in the presence of
inert gases. Data at 2000 K are given for a single
experiment.
NH3  NH2 + H
t (hours)
[NH3] (mol/L)
0
8.000 x 10-7
25
6.75 x 10-7
50
5.84 x 10-7
75
5.15 x 10-7
Plot the appropriate concentration expressions
against time to find the order of the reaction. Find
the rate constant of the reaction from the slope of
the line. Use the given data and the appropriate
integrated rate equation to check your answer.
24. A certain first-order reaction has a rate constant
k=1.6x10-3 s-1. What is the half-life for this
reaction?
25. The decomposition of NOCl, the compound that
gives a yellow-orange color to aqua regia (a
mixture of concentrated HCl and HNO3 that’s
able to dissolve gold and platinum) follows the
reaction 2NOCl 2NO + Cl2. It is a second-order
reaction with k=6.7x10-4 M-1 s-1 at 400K. What is
the half-life of this reaction if the initial
concentration of NOCl is 0.20 M?
5
29. The following data were obtained from a study
of the decomposition of a sample of HI on the
surface of a gold wire. (a) Plot the data to find
the order of the reaction, the rate constant, and
the rate equation. (b) Calculate the HI
concentration in mmol/L at 600 seconds.
t (seconds) [HI] (mmol/L)
0
5.46
250
4.10
500
2.73
750
1.37
32. The following data were measured for the
reaction BF3 (g) + NH3 (g) F3BNH3 (g)
[BF3] (M)
[NH3] (M)
1
2
3
4
5
0.250
0.250
0.200
0.350
0.175
0.250
0.125
0.100
0.100
0.100
Initial Rate
(M/s)
0.2130
0.1065
0.0682
0.1193
0.0596
a. What is the rate law for the reaction?
b. What is the overall order of the reaction?
c. What is the value of the rate constant for the
reaction?
30. The dimerization of butadiene
2C4H6(g)  C8H12(g)
was studied at 500 K, and the following data were
obtained.
Time (s)
195
604
1246
2180
6210
Expt
33. The reaction
A  B + C is known
to be zero order in A and to have a rate
constant of 5.0x10-2 mol/L◦s at 25°C where
[C4H6] (mol/L)
1.6 x 10-2
1.5 x 10-2
1.3 x 10-2
1.1 x 10-2
0.68 x 10-2
[A]0=1.0x10-3 M.
a. Write the integrated rate law for this
reaction.
b. Calculate the half-life for the reaction
c. Calculate the concentration of B after
5.0x10-3s has elapsed.
Assuming: Rate= -∆[C4H6]/ ∆t, determine the form
of the rate law, the integrated rate law, and the rate
constant for this reaction. (These are actual
experiments so the line may not be perfectly
straight.)
34. The radioactive isotope 32P decays by first-order
kinetics and has a half-life of 14.3 days. How long
does it take for 95.0% of a sample for 32P to
decay?
31. The rate of the reaction
O(g)+NO2(g)NO(g)+O2(g)
was studied at a certain temperature. In the first set
of experiments, NO2 was in large excess, at a
concentration of 1.0x1013 molecules/cm3 with the
following data collected:
Time(s)
[O] (atoms/cm3)
0
5.0x109
1.0x10-2
1.9x109
-2
2.0x10
6.8x108
3.0x10-2
2.5x108
35. A first-order reaction is 38.5% complete in 480s
a. Calculate the rate constant?
b. What is the value of the half-life?
c. How long will it take for the reaction to go
to 25%, 75%, and 95% completion?
36. It took 143 s for 50.0% of a particular substance
to decompose. If the initial concentration was
0.060 M and the decomposition reaction follows
second-order kinetics, what is the value of the
rate constant?
a. What is the order of the reaction with respect to
oxygen atoms?
b. The reaction is known to be first order with
respect to NO2. Determine the overall rate law and
the value of the rate constant.
6
The decomposition of SO2Cl2 in the gas phase, SO2Cl2  SO2 + Cl2
can be studied by measuring the concentration of Cl2 as the reaction proceeds.
We begin with [SO2Cl2]0 = 0.250 M.
37.
Holding the temperature constant at 320oC, we monitor the Cl2 concentration, with the following results.
t(hours)
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
[Cl2] (mol/L)
0.000
0.037
0.068
0.095
0.117
0.137
0.153
0.168
0.180
0.190
0.199
Plot [Cl2] versus t. (b) Plot [SO 2Cl2] versus t. (c) Determine the rate law for this reaction. (d) What is
the value, with units, for the specific rate constant at 320°C? (e) How long would it take for 95% of
the original SO 2Cl2 to react?
Arrhenius Equation
T (K)
273
280
290
300
310
320
330
340
350
360
370
T (°C)
25.0
30.0
k
4.18E-05
9.68E-05
2.00E-04
8.60E-04
2.31E-03
5.82E-03
1.39E-02
3.14E-02
6.80E-02
1.41E-01
2.81E-01
38.
Temperature Dependence of Rate Constant for Iodide Plus Bromomethane
Reaction
Calculate the frequency factor and the activation energy.
39.
These data were obtained for the rate constant for reaction of an
unknown compound with water:
K (s1-)
7.95x10-8
2.37 x10-7
T (°C)
56.2
78.2
k (s1-)
1.04x10-5
1.45 x10-4
a. Calculate the activation energy and
frequency factor for this reaction.
b. Estimate the rate constant of the reaction
at a temperature of 100.0°C
7