CHAPTER 12 HOMEWORK

1. Read Chapter 12, sections 1, 2

2. A graph of [In ] vs time was interpolated at two different times. The results are shown+

below. Calculate the average rate of the reaction during this time interval.

Answer: 5.7 x 10 M/s-6

3. The slope of the [A] vs time graph was determined at 176 seconds. The value is shown inthe dialog box on the graph. What is the instantaneous rate of the reaction at 176seconds?

4. End of Chapter Problems: 21, 23, 24

5. Read sections 2,3. End of Chapter problems: 25, 26, 27, 29, 31.

End Exam 1---------------------------------------------------------------------------------------------------------------------

6. Read section 4. End of Chapter problems: 33, 35, 37, 39, 41

Answer: 3.84 x 10 M/s-6

7. The kinetics of the decomposition of dinitrogen pentoxide was studied and the data isdisplayed in graphical form below.

2 5a. What is the order of the reaction with respect to N O ?

2 5b. What was the initial concentration of N O ?

c. What is the value of the rate constant with units?

d. What is the value of the initial rate of the reaction?

e. If the rate of the reaction is 8.7 x 10 M/s, what is the current concentration of-5

2 5N O ?

Answers: a. 1 b. 0.035 M c. 9.892 x 10 1/sst -4

d. 3.46 x 10 M/s e. 0.088 M-5

f. What is the half life of the reaction?

2 5g. What fraction of the initial N O would remain after 2 minutes?

2 5h. What is the concentration of N O at 60 seconds?

2 5i. If the concentration of N O is measured to be 0.0200 M, how much time haselapsed since the beginning of the experiment?

Answers: f. 700 s g. 0.89 h. 0.033 M i. 566 s

8. End of Chapter Problems: 43, 45, 47, 49, 51, 57, 97, 103

9. Shown below is the distribution of energies at 300 K and 350 K.

The above graph is integrated starting from 30 kJ/mol and then again starting from 60 kJ/mol andthe results are shown below along with expanded views of the graphs.

a. Suppose the activation energy of reaction A is 30 kJ/mol. What fraction of themolecules at 300 K and 350 K have enough energy to react?

b. If the activation energy of another reaction, reaction B, is 60 kJ/mol, what fractionof the molecules at 300 K and 350 K have enough energy to react?

c. If the temperature is raised from 300 K to 350 K, by what factor would you expectthe rate of reaction A to increase?

d. If the temperature is raised from 300 K to 350 K, by what factor would you expectthe rate of reaction B to increase?

e. At 300 K, how many times faster is reaction A than reaction B?

f. At 350 K, how many times faster is reaction A than reaction B?

g. As temperature increases, although reaction A is still faster than reaction B, what ishappening to the difference in the reaction rates of A and B?

Answers: a. 2.4 x 10 , 1.3 x 10-5 -4

b. 2 x 10 , 5.8 x 10-10 -9

c. 5.4d. 29e. 120,000f. 22,000g. The two reactions are getting closer to having the same rate.

End Quiz 2--------------------------------------------------------------------------------------------------------------------

10. Read sections 5,6,7. End of Chapter Problems: 61, 63, 65, 81, 89

11. The rate of reaction of the following reaction was studied and the data obtained is shownin the table:

2Ar + O ------> Ar + O + O

Temperature (K) k (L mol s )-1 -1

5,000 5.49 x 106

10,000 9.86 x 108

15,000 5.09 x 109

18,000 8.60 x 109

1. Graphically determine the activation energy of the reaction.2. Graphically determine the value of A for the reaction.3. What fraction of the collisions at 298 K would have enough energy for reaction?4. Calculate the value of k at 298 K from the Arrhenius equation.

a5. Considering the E , how fast would you expect this reaction be at roomtemperature?

6. Would the slope of graph be steeper, less steep or not effected if a catalyst wereadded?

12. End of Chapter Problems: 53, 55, 57, 69, 71

ANSWERS:

1. 425 kJ/mol

2. 1.5 x 1011

3. 3.4 x 10-75

4. 5.1 x 10-64

5. effectively it wouldn’t react

a a6. less step since slope = -E /R and E

is less