Kinetics Practice Problems

Note: The problems below have been pulled from various exams I have given over the years. You might see these problems again when the exams from which they have been taken are posted in their entirity.

1. The reaction

     2NO2(g)      +      F2(g)      ---------->      2NO2F(g)

was studied by measuring its initial rate for varying initial concentrations of NO2 and F2. The following table gives the results of three such experiments.
Expt. #[NO2]initial[F2]initialRate
10.0125 M0.0253 M0.0560 M / s
20.0250 M0.0253 M0.1120 M / s
30.0125 M0.0506 M0.1120 M / s
Which of the following is the correct rate law for the reaction?

a) Rate = 215 M-2 s-1[NO2]2[F2]

b) Rate = 385 M-2 s-1 [NO2][F2]2

c) Rate = 514 M-2 s-1 [NO2]2[F2]

d) Rate = 177 M-1 s-1 [NO2][F2]

e) Rate = 673 M-3 s-1 [NO2]2[F2]2

2. The reaction

     2NO2(g)      +      F2(g)      ---------->      2NO2F(g)

was studied by measuring its initial rate for varying initial concentrations of NO2 and F2. The following table gives the results of three such experiments.
Expt. #[NO2]initial[F2]initialRate
10.0125 M0.0253 M0.0280 M / s
20.0250 M0.0253 M0.0560 M / s
30.0125 M0.0506 M0.0560 M / s
Which of the following is the correct rate law for the reaction?

a) Rate = 88.5 M-1s-1 [NO2] [F2]

b) Rate = 12.5 M-2 s-1 [NO2]2 [F2]

c) Rate = 12.5 M-2 s-1 [NO2] [F2]2

d) Rate = 38.7 M-3 s-1 [NO2]2 [F2]2

e) Rate = 42.8 s-1 [F2]

3. The reaction

     2NO2(g)      +      F2(g)      ---------->      2NO2F(g)

was studied by monitoring its initial rate under varying conditions of reactant concentrations. The results of three such experiments are presented in the following table:

Expt. #[NO2]initial[F2]initialRate
13.4 x 10-3 M3.2 x 10-3 M1.8 x 10-5 M/s
26.8 x 10-3 M3.2 x 10-3 M3.6 x 10-5 M/s
33.4 x 10-3 M6.4 x 10-3 M3.6 x 10-5 M/s
Which of the following is the correct rate law for the reaction, based on the above data?

     a) R = (1.65 / M s) [NO2] [F2]

     b) R = (487 / M2 s) [NO2]2 [F2]

     c) R = (517 / M2 s) [NO2] [F2]2

     d) R = (1.52 x 105 / M3 s) [NO2]2 [F2]2

     e) R = (1.43 x 105 / M3 s) [NO2]2 [F2]2

4. What statement can be made about the chemical reaction in problem 3?

     a) The reaction definitely MUST be elementary

     b) The reaction definitely must NOT be elementary

     c)The reaction could possibly be elementary, but we can't be sure

5. The reaction

     2NO(g)      +      H2(g)      ---------->      N2O(g)      +      H2O(g)

was studied by the initial rate method to determine the rate law. The following table gives the results of three experiments, all conducted at the same temperature. Determine the orders of reaction with respect to NO and H2 and determine the rate constant. Using this information, write the complete rate law for the reaction. (Note: For this problem, ficticious data may be used, so it is possible to get, for example, a fourth order concentration dependence without there being any thing wrong with your calculation)
Expt. #[NO]0[H2]0Rate
11.17 x 10-3 M4.30 x 10-3 M1.05 x 10-5 M/s
23.51 x 10-3 M4.30 x 10-3 M9.45 x 10-5 M/s
31.17 x 10-3 M8.60 x 10-3 M4.20 x 10-5 M/s
No multiple choice answers for this one. You write out the rate law on your own. Answer is provided at the end of the test.

6. Based on the rate law you determined for the reaction in problem 5, which of the following is a correct statement? (Note: Base your answer solely on your rate law, and the reaction given in the problem, and not on the reasonableness that such a reaction could actually occur in a single step. The problem may be using a ficticious reaction and / or ficticious data.

     a) The reaction in problem 5 definitely MUST be elementary

     b) The reaction in problem 5 definitely must NOT be elementary

     c) The reaction in problem 5 could possibly be elementary, but we can't be sure

7. The reaction

     SO2Cl2(g)      ---------->      SO2(g)      +      Cl2(g)

is first order with respect to SO2Cl2. This reaction was run at a temperature at which the rate constant was 1.3 x 10-5 /s. In an experiment, a sample of SO2Cl2 at a concentration of 0.0316 mol/L was allowed to decompose by the reaction described above. What was the concentration of SO2Cl2 5.75 hours after the start of the reaction?

     a) 0.002 mol / L      b) 0.014 mol / L      c) 0.024 mol / L

     d) 0.0305 mol / L      e) 0.0312 mol / L

8. If a chemical reaction occurs 2 times faster at 40 oC than it does at 30 oC, what is the activation energy of the reaction?

     a) 21.5 kJ / mol      b) 33.8 kJ / mol      c) 41.2 kJ / mol

     d) 54.7 kJ / mol      e) 72.1 kJ / mol

ANSWERS:

1 d      2 a      3 a      4 b

5      R = 4.15 x 105 M-3 s-1 [NO]2 [H2]2

6 b      7 c      8 d

This page was last modified Tuesday March 2, 1999