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Exam III Thursday, December 7, 7:00-9:00 pm; rooms are on the website. Conflict: (12/7) 4:30-6:30 pm in 101 Transportation; sign up in 1026 Chem Annex Conflict with conflict? Email me right away. Review sessions: To be announced

Rate Laws From Elementary Steps

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

Clicker Question The experimental rate law for the decomposition of nitrous oxide (N2O) to N2 and O2 is rate = k[N2O]2. Two mechanisms are proposed: I. N2O  N2 + O N2O + O  N2 + O2 II. 2N2O N4O2 N4O2  2N2 + O2 Which of the following could be a correct mechanism? a) Mechanism I with the first step as the rate-determining step. b) Mechanism I with the second step as the rate-determining step as long as the first step is a fast equilibrium step. c) Mechanism II with the second step as the rate-determining step if the first step is a fast equilibrium step. d) None of the choices (a-c) could be correct. e) At least two of the above choices (a-c) could be correct.

Pseudo-Order Question Determine the rate law and value of k given the following data. 2H2(g) + 2NO(g)  N2(g) + 2H2O(g) EXPERIMENT #1 EXPERIMENT #2 TIME (sec) [NO] [NO] ________ 0 1.00 x 10-2 M 1.00 x 10-2 M 10.0 6.67 x 10-3M 5.00 x 10-3 M 20.0 5.00 x 10-3 M 3.33 x 10-3 M 30.0 4.00 x 10-3 M 2.50 x 10-3 M 40.0 3.33 x 10-3 M 2.00 x 10-3 M   In experiment #1, [H2]0 = 10.0 M In experiment #2, [H2]0 = 20.0 M