1. Lon-Capa 8th (final) HW assignment due Tuesday, December 2 by 5 pm.
Quiz #6 opens Friday at 5 pm. Due Tuesday, December 2 by 10 pm.
Exams and Practice Exams on website

2. Clicker Question [A] Time 1.00 M 0.500 M 10 sec 0.250 M ?? sec
Determine the missing time given the following orders of reaction for
aA  Products
zero 1st 2nd a) b) c)
d) Not sure.
[A]
Time
1.00 M
0.500 M
10 sec
0.250 M
?? sec

3. Chapter 15: 102 Time (s) Ptotal (torr) 250. 10. 265 20. 280. 30. 295
250.
10.
265
20.
280.
30.
295
40.
310.
50.
325
The following results were obtained at 600K for the decomposition of ethanol on an alumina (Al2O3) surface,
C2H5OH(g)  C2H4(g) + H2O(g)
a. Predict Ptotal in torr at t = 80. s
b. What is the value of the rate constant, and what are the units?
c. What is the order of the reaction?
d. Calculate Ptotal at t = 300. s

4. aA + bB  Products
Given the following data, determine the rate law and the value for the rate constant.
Expt 1 {[B] = 5.00 M} Expt 2 {[B] = 10.0 M}
[A]
time
0.010 M M
40. sec M
120 sec.
[A]
time
0.010 M M
20. sec M
60. sec

5. Mechanisms Series of elementary steps. Must be chemically reasonable
Must have the correct stoichiometry. That is, the steps must add up to the overall reaction.
Must be chemically reasonable
How can we tell this?
Cannot prove but can support empirically.
Must agree with the overall rate law.

6. Rate Laws From Elementary Steps

7. Evaluating Mechanisms
The rate law comes from the rate-determining step (the “slow” step).
Fast equilibrium.
Rate forward = rate reverse.
Rate law cannot include intermediates.
Steady-state approximation.
[intermediate] = constant.
d[intermediate]/dt = 0

8. Chapter 15: 115
Do for next Friday.