Exam 2 Version A Key

Exam 2 Version A Key - Chemistry 1515, Midterm Exam #2,...

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Unformatted text preview: Chemistry 1515, Midterm Exam #2, Version A March 2, 2011 This exam is closed book, notes, papers, etc. You may use a calculator. If you need a physical constant or unit conversion factor that is not provided, please ask. This exam must represent your own work. Put your answers on an orange scantron form. Useful Information R = 8.314 J/mol K = 0.0821 L atm/mol K N A = 6.022 x 10 23 mol-1 1 atm = 760 Torr CHEM 1515, Spring 2011 Midterm Exam #2, Version A Page 2 1. Which exam version do you have? 2. An increase in temperature increases the reaction rate because A. a greater fraction of the collisions have the correct orientation of molecules. B. the activation energy of the reaction will increase. C. the activation energy of the reaction will decrease. D. temperature acts as a catalyst in chemical reactions. E. more collisions will have enough energy to exceed the activation energy. 3. The following reaction mechanism is proposed for for the reaction of H 2 ( g ) with NO( g ): ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) g O H g N g H g O N g O H g O N g H g O N g O N g NO k k k k 2 2 2 2 2 2 2 2 2 2 2 3 2 1 1 2 + + + + The second step is slow compared to the other steps. Consider the following statements, based on only the information provided: I. The overall reaction is ( ) ( ) ( ) ( ) g O H g N g NO g H 2 2 2 2 2 2 + + II. The overall rate law for this mechanism is [ ] [ ] 2 2 1 2 1 NO H k k k R = . III. An increase in temperature will definitely increase the overall reaction rate. A. Only statement I is correct. B. Only statement II is correct. C. Only statement III is correct. D. Only statements I and II are correct. E. Only statements I and III are correct. 4. Which of the following has an effect on the magnitude of the equilibrium constant? A. removing products as they are formed B. adding more of a reactant C. adding a catalyst D. increasing the pressure, in a gas-phase reaction E. change in temperature 5. Consider this reaction: 2NH 3 (g) N 2 (g) + 3H 2 (g) If the rate [H 2 ]/ t is 0.030 mol L 1 s 1 , then [NH 3 ]/ t is: A. -0.045 mol L 1 s 1 B. -0.030 mol L 1 s 1 C. -0.020 mol L 1 s 1 D. -0.010 mol L 1 s 1 E. None of these choices is correct. CHEM 1515, Spring 2011 Midterm Exam #2, Version A Page 3 6. Hydrogen sulfide will react with water as shown in the following reactions. What is the value of K 2 ? A. 1.3 10 27 B. 2.3 10 7 C. 1.3 10 13 D. 7.7 10 12 E. 7.7 10 26 7. A student adds 0.1 mol of oxalic acid and 0.1 mol of sodium dihydrogen phosphate to enough water to make 1.0 L of solution. The following equilibrium is established with the concentrations of the products greater than the concentrations of the reactants. Which of the statements about the equilibrium system is correct?...
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Exam 2 Version A Key - Chemistry 1515, Midterm Exam #2,...

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