TERNANSKY Midterm 1 2007 SU

TERNANSKY Midterm 1 2007 SU - Chemistry 140A Summer, 2007...

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Unformatted text preview: Chemistry 140A Summer, 2007 First Midterm Exam-250 points 7/12/07 DO NOT OPEN THIS EXAM UNTIL INSTRUCTED TO DO SO.....FILL OUT THE FOLLOWING INFORMATION NOW : . YOUR NAME (Print): Ima Key PID: _________________________________________________ SIGNATURE: _________________________________________ ID checker initials: ____________________ If you wish to have any answers considered for a re-grade, your exam must be completed in INK . 1. (10 points) Draw the BEST Lewis dot structure for nitromethane: (CH 3 NO 2 ). Be sure to indicate charges where appropriate. Use straight lines for bonds and dots for unshared electron pairs. H C N O O H H H 3 C N O O 10 pts 8 pts 2. (18 points) Draw the TWO MAJOR (best) resonance contributors for BrO 2- (OBrO)- . Be sure to indicate charges where appropriate. Use straight lines for bonds and dots for unshared electron pairs. Make appropriate use of curved arrows to indicate electron movement. O Br O O Br O brackets: 2 pts double headed arrow: 2 pts 5 pts structure 2 pts each curved arrow 5 pts structure 3. (30 points) Consider the following reaction coordinate-energy diagram drawn for the reaction shown: A B + C D + E step 1 step 2 RC B+C A TS-2 TS-1 D+E E E a1 E a2 20 kcal (3 pts) Is step #1 of the sequence exothermic or endothermic? (circle your choice) (3 pts) Is the overall reaction (from A to D + E) exothermic or endothermic? (circle your choice) (3 pts) If the activation energy for step #2 (E a2 ) was MORE that the activation energy of step #1 (E a1 ), would the overall reaction be exothermic or endothermic? (circle your choice)...
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TERNANSKY Midterm 1 2007 SU - Chemistry 140A Summer, 2007...

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