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

2 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 Rate law cannot include intermediates.

3 Clicker Question The reaction 2A + B  C has the following proposed mechanism A + B D (fast equil.) D + B  E (slow) E + A  C + B(fast) The rate law from this mechanism is a) rate = k[A][B] d) rate = k[A][B] 2 b) rate = k[A] 2 [B] e) I don’t know c) rate = k[A] 2 [B] 2 d) rate = k[A][B] 2

4 Reaction Profiles

5 Recall for 1 st Lecture

6 Transition State

7 Rate constant (k) vs. T

8 ln(k) vs. 1/T

9 Catalyzed Pathways Have a Lower Activation Energy

10 Catalyzed Pathways Have a Lower Activation Energy

11 Zero-order (catalyst)

12 Chapter 15: 115 Consider the hypothetical reaction: A + B + 2C  2D + 3E In a study of this reaction, three experiments were run at the same temperature. The rate is defined as –d[B]/dt. Expt 1: [A] 0 = 2.0 M, [C] 0 = 1.0 M, [B] 0 = 1.0 x M Write the rate law for this reaction, and calculate the rate constant. [B] (mol/L) Time (s) 2.7 x x x x x x x x x x x x 10 5

13 Chapter 15: 115 Consider the hypothetical reaction: A + B + 2C  2D + 3E In a study of this reaction, three experiments were run at the same temperature. The rate is defined as –d[B]/dt. Expt 2: [B] 0 = 3.0 M, [C] 0 = 1.0 M, [A] 0 = 1.0 x M Write the rate law for this reaction, and calculate the rate constant. [A] (mol/L) Time (s) 8.9 x x x x x x

14 Chapter 15: 115 Consider the hypothetical reaction: A + B + 2C  2D + 3E In a study of this reaction, three experiments were run at the same temperature. The rate is defined as –d[B]/dt. Expt 3: [A] 0 = 10.0 M, [B] 0 = 5.0 M, [C] 0 = 5.0 x M Write the rate law for this reaction, and calculate the rate constant. [C] (mol/L) Time (s) x x x x x x 10 -2