Chemistry 162
Kinetics On the Board
April12, 2016
1. For the reaction A + 2B → 2C, the rate of reaction is 1.76X10-5 s-1 at the time when [A] = 0.3580 M.
a. What is the rate of formation of C?
b. What will [A] be 1.00 min later?
c. Assume the rate remains at 1.76 X 10-5 M/s. How long would it take for [A] to change from
0.3580 to 0.3500 M?
2. In three different experiments, the following results were obtained for the reaction A → products:
[A]0 = 1.00M, t1/2 = 50 min; [A]0 = 2.00 M, t1/2 = 25 min; [A]0 = 0.50 M, t1/2 = 100 min. Write the rate
equation for this reaction, and indicate the value of k.
3. Potassium chlorate decomposes via a first order reaction with a half life of 144 min.
a. How long will it take for a sample of potassium chlorate acid to be 65% decomposed?
b. How many liters of Oxygen, measured at 24. 5°C and 748 torr, are produced as a 10.0 g sample
of potassium chlorate decomposes for 575 minutes?
4. For the reversible reaction A + B ↔ C + D, the enthalpy change of the forward reaction is 21 kJ/mole.
The activation energy of the forward reaction is 84 kJ/mole. What is the activation energy of the reverse
reaction.
5. A commonly stated rule of thumb is that reaction rates double for a temperature increase of about 10°C,
which is often wrong. What must be the appropriate activation energy for this statement to be true for
reactions at about room temperature?
6. A simplified rate law for the reaction 2O3 → 3O2 is R = k[O3]2/[O2]. For this reaction, propose a
two-step mechanism that consists of a fast, reversible first step, followed by a slow second step.