AP Chemistry 12
Chemical Kinetics: Problem Set A (Measuring Reaction Rates & Rate Laws)
1.
What are the relative rates for each reactant and product in the decomposition of
nitrosyl chloride (NOCl)? The reaction is:
2NOCl  2NO + Cl2
2.
What would be the rate of formation of CO2 if the concentration of octane, C8H18
was changing at a rate of 0.25 mol L-1 s-1 during the combustion of octane?
3.
When the concentration of a particular reactant was increased by a factor of 10, the
reaction rate was increased by a factor of 1000. What is the order of the reaction
with respect to that reactant?
4.
A certain reactant disappears by a first-order reaction that has a rate constant
k = 3.5 x 10-3 s-1. If the initial concentration of the reactant is 0.500 M, how long
will it take for the concentration to drop to 0.200 M?
5.
Can vegetarians eat animal crackers?
6.
A certain first-order reaction has a half-life of 30 minutes. What is the rate constant
for the reaction?
7.
In dilute NaOH at 20 C, the decomposition of hydrogen peroxide (H2O2) is firstorder in H2O2 only, and the rate constant is 1.00 x 10-3 min-1. If the initial
concentration of H2O2 is 0.020 M, what is its concentration after exactly 100
minutes?
8.
The reaction
2NO(g)
+
Cl2(g)  NOCl(g)
was studied at -10C. The following results were obtained where rate = - [Cl2]/t
[NO]0 (M)
0.10
0.10
0.20
[Cl2]0 (M)
0.10
0.20
0.20
a) What is the rate law?
b) What is the value of the rate constant?
Initial rate (M.min-1)
0.18
0.36
1.45
AP Chemistry 12
9.
A dimer is a molecule composed of two identical molecules. Butadiene (C4H6)
reacts to form its dimer according to the equation:
2C4H6(g)  C8H12(g)
The following data were collected for this reaction at a given temperature:
[C4H6] (M)
0.01000
0.00625
0.00476
0.00370
0.00313
0.00270
0.00241
0.00208
Time (s)
0
1000
1800
2800
3600
4400
5200
6200
a) Is this reaction first-order or second-order? (HINT: Plot a graph)
b) What is the value of the rate constant for the reaction?
c) What is the half-life for the reaction under the conditions of this experiment?
10. The reaction
2HI  H2 + I2
is second-order with respect to HI. At 508C, k = 0.079 L mol-1 s-1.
a) Write the rate law for this reaction.
b) What is the half-life for this reaction at 508C when initially [HI] = 0.050M?
Answers:
1. rate = -1/2[NOCl]/t = 1/2[NO]/t = [Cl2]/t
2.
2.0 mol L-1 s-1
6.
3.8 x 10-4 s-1
7.
0.018 M
8.
a) rate = k[NO] 2[Cl2]
9.
a) 2nd order
10. a) rate = k[HI] 2
3.
3rd order
4. 2.6 x 102 s
5. laugh!
b) 1.8 x 102 L2 mol-2s-1
b) 6.14 x 10-2 L mol-1s-1
b) 2.5 x 102s
c) 1630 s