HW9solutions - Niu (qn269) Homework 9 flowers (53885) 1...

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Unformatted text preview: Niu (qn269) Homework 9 flowers (53885) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. Homework 9. Due 05 December 2008 at 11PM. Solutions available 05 December 2008 at 11:15 PM 001 10.0 points Which of the following statements about re- acting molecules is true? 1. When two reactant molecules collide they must react. 2. All molecules in a gas sample at a specific temperature have the same energy. 3. The transition state energy is usually the average between the energies of the reactants and products. 4. An effective collision between two molecules must be oriented correctly. cor- rect Explanation: A collision between molecules results in a reaction if they collide with enough energy and an effective orientation. 002 10.0 points The fraction of molecules that collide with a kinetic energy equal to the activation en- ergy for a reaction decreases rapidly with an increase in temperature. 1. True 2. False correct Explanation: 003 10.0 points Increasing the temperature of a reaction causes ? in the reaction rate. 1. You need to know H for the reaction. 2. an increase correct 3. no change 4. a decrease Explanation: At increased temperature more heat is pro- vided to the reaction components, so the num- ber of effective collisions increase. 004 10.0 points Consider the following potential energy dia- gram. e f c d a b A+B X+Y Reaction progress Potentialenergy Which arrow represents the activation en- ergy? 1. d 2. b correct 3. f 4. e 5. a 6. c Explanation: Definition 005 (part 1 of 4) 10.0 points Consider the following potential energy dia- gram. Niu (qn269) Homework 9 flowers (53885) 2 a b d c e f g A+B X+Y Reaction progress Potentialenergy Which arrow represents the potential en- ergy of the reactants? 1. d 2. f 3. e 4. c 5. g 6. b 7. a correct Explanation: Recall 006 (part 2 of 4) 10.0 points Which arrow represents the potential energy of the products? 1. e 2. c 3. a 4. b 5. d 6. f 7. g correct Explanation: Recall 007 (part 3 of 4) 10.0 points Which arrow represents the activation en- ergy? 1. d 2. e 3. f 4. c 5. a 6. b correct 7. g Explanation: Recall 008 (part 4 of 4) 10.0 points Which arrow represents the heat of reaction (enthalpy change)? 1. e 2. b 3. a 4. g 5. d 6. c correct 7. f Explanation: Recall 009 10.0 points A catalyst 1. cannot be a biological molecule like an enzyme. Niu (qn269) Homework 9 flowers (53885) 3 2. increases the rate of a chemical reaction but is not consumed in the process. correct 3. operates only at high temperatures. 4. never occurs naturally; it is man-made. 5. must always be solid, as in a catalytic converter....
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This note was uploaded on 02/04/2009 for the course CH 53885 taught by Professor Flowers during the Fall '08 term at University of Texas at Austin.

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HW9solutions - Niu (qn269) Homework 9 flowers (53885) 1...

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