Lon-Capa

8th (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

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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.

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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 isa) 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

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Reaction Profiles

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Recall for 1st Lecture

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Transition State

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Rate constant (k) vs. T

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ln(k) vs. 1/T

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Catalyzed Pathways Have a Lower Activation Energy

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Catalyzed Pathways Have a Lower Activation Energy

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Zero-order (catalyst)

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Chapter 15: 115Consider the hypothetical reaction:

A + B + 2C 2D + 3EIn 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 10-3 M

Write the rate law for this reaction, and calculate the rate constant.

[B] (mol/L)

Time (s)

2.7 x 10-

4

1.0 x 105

1.6 x 10-

4

2.0 x 105

1.1 x 10-

4

3.0 x 105

8.5 x 10-

5

4.0 x 105

6.9 x 10-

5

5.0 x 105

5.8 x 10-

5

6.0 x 105

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Chapter 15: 115Consider the hypothetical reaction:

A + B + 2C 2D + 3EIn 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 10-2 M

Write the rate law for this reaction, and calculate the rate constant.

[A] (mol/L)

Time (s)

8.9 x 10-

3

1.0

7.1 x 10-

3

3.0

5.5 x 10-

3

5.0

3.8 x 10-

3

8.0

2.9 x 10-

3

10.0

2.0 x 10-

3

13.0

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Chapter 15: 115Consider the hypothetical reaction:

A + B + 2C 2D + 3EIn 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 10-1 M

Write the rate law for this reaction, and calculate the rate constant.

[C] (mol/L)

Time (s)

0.43 1.0 x 10-

2

0.36 2.0 x 10-

2

0.29 3.0 x 10-

2

0.22 4.0 x 10-

2

0.15 5.0 x 10-

2

0.08 6.0 x 10-

2