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Exam III Thursday, December 6, 7:00-9:00 pm; rooms are on the website (same as Exam II). Conflict: (12/6) 4:30-6:30 pm in 219 Greg; sign up in 1026 Chem Annex starting Friday Conflict with conflict? Email me right away. Review sessions: 1024 Chem Annex, 6-8 pm Monday, December 3 Tuesday, December 4

Remaining Lectures Wednesday, December 5: review for Exam 3. Friday, December 7: go over Exam 3. Monday, December 10: review the semester; discuss the final exam; revisit demonstrations. Wednesday, December 12: no lecture; office hours in 3014 Chem Annex from 10am-12pm.

Chapter 15

Chapter 15 #91

Previous Exam Question Consider the “Magic Genie” demonstration, in which hydrogen peroxide decomposed to water and oxygen gas with the aid of a catalyst. The activation energy of this reaction (uncatalyzed) is 70.0 kJ/mol. We added a catalyst that lowered the activation energy (at 20C) to 42 kJ/mol. Theoretically, to what temperature (C) would we have to heat the hydrogen peroxide solution so that the rate of the uncatalyzed reaction was equal to the rate of the catalyzed reaction? Assume the frequency factor A to be constant.

Previous Exam Question (pt 1) Pure N2O was placed in a rigid vessel and allowed to decompose. The following data were collected in an experiment at a constant temperature of 298K. Assume the rate of the reverse reaction is negligent in this problem. 2N2O(g)  2N2(g) + O2(g) rate = –d[N2O]/dt Determine the rate law for the reaction including the order of the reaction and the value (with units) for the rate constant. Time (min) Ptotal (atm) 1.000 10.00 1.125 20.00 1.218 30.00 1.288 40.00 1.341 50.00 1.381

Previous Exam Question (pt 2) Pure N2O was placed in a rigid vessel and allowed to decompose. The following data were collected in an experiment at a constant temperature of 298K. Assume the rate of the reverse reaction is negligent in this problem. 2N2O(g)  2N2(g) + O2(g) rate = –d[N2O]/dt Determine the partial pressure of N2(g) at 110.0 min. Time (min) Ptotal (atm) 1.000 10.00 1.125 20.00 1.218 30.00 1.288 40.00 1.341 50.00 1.381

Previous Exam Question (pt 3) Pure N2O was placed in a rigid vessel and allowed to decompose. The following data were collected in an experiment at a constant temperature of 298K. Assume the rate of the reverse reaction is negligent in this problem. 2N2O(g)  2N2(g) + O2(g) rate = –d[N2O]/dt The reaction is carried out again at 303K. The first half-life is noted to be at 4.58 min. Determine the activation energy of the reaction. Time (min) Ptotal (atm) 1.000 10.00 1.125 20.00 1.218 30.00 1.288 40.00 1.341 50.00 1.381

Previous Exam Question (pt 4) The formula of the reactant, N2O, doesn’t tell us if the skeletal structure is N-O-N or N-N-O, nor does it tell us if there is a best Lewis structure. Your goal is to find the best Lewis structure for the compound, using formal charge as the primary basis. Justify your answer completely.

Previous Exam Question (pt 5) Using the bond energies below and your answers to parts 1, 3, and 4, develop a mechanism for the reaction and support your answer. 2N2O(g)  2N2(g) + O2(g) rate = –d[N2O]/dt Bond Bond Energy (kJ/mol) N–O 201 N=O 607 N=N 418 N≡O 941