CHEM1310F11_Final-Answers

CHEM1310F11_Final-Answers - CHEM 1310 Final Exam December...

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CHEM 1310 Final Exam 3 hour exam December 14, 2011 Page 1 of 13 Answer Key, Part A 1. Which one of the following statements is true? a. Energy is released when chemical bonds are broken. b. Heat and work are state functions. c. For reaction processes that involve gases, Δ E and Δ H are always equal. d. The expansion of a system at constant temperature gives Δ E sys > 0. e. The molar heat capacity of a pure substance depends on its phase. 2. The balanced chemical equation that is associated with o f H , the standard enthalpy of formation for HCl ( g ), is: a. H ( g ) + Cl ( g ) HCl ( g ) b. H 2 ( g ) + Cl 2 ( g ) 2 HCl ( g ) c. ½ H 2 ( g ) + ½ Cl 2 ( g ) HCl ( g ) d. H 2 ( g ) + Cl 2 ( l ) 2 HCl ( g ) e. ½ H 2 ( g ) + ½ Cl 2 ( l ) HCl ( g ) 3. Metals have similar molar heat capacities. For example, aluminum, copper, magnesium, and silver have molar heat capacities of 24.2, 24.5, 24.9, and 24.9 J K –1 mol –1 , respectively. Which one of these metals would require the least amount of heat energy to change the temperature of a 10 g sample by 10°C? a. Aluminum b. Copper c. Magnesium d. Silver e. All four metals will require approximately the same amount of heat energy. 4. Which one of the following processes is not spontaneous? a. A process for which the change in free energy is negative. b. A process for which the electrical potential is positive. c. A process that is exothermic and that results in an increase in entropy. d. A process for which the there is an increase in total entropy. e. None of the above: all of these processes are spontaneous. 5. Which reaction is accompanied by an increase in entropy? a. Zn (s) + ½ O 2 (g) ZnO (s) b. CH 4 (g) + H 2 O (g) CO (g) + 3 H 2 (g) c. BaO (s) + CO 2 (g) BaCO 3 (s) d. Na 2 CO 3 (s) + CO 2 (g) + H 2 O (g) 2 NaHCO 3 (s) e. N 2 (g) + 3 H 2 (g) 2 NH 3 (g)
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CHEM 1310 Final Exam 3 hour exam December 14, 2011 Page 2 of 13 6. At 25°C, 62.44 kJ mol –1 of heat is absorbed when solid iodine sublimes to form iodine vapour. What is the change in entropy of the system when 0.500 mol of iodine sublimes at 25°C? a. 31.22 kJ mol –1 b. 2500 J K –1 mol –1 c. 1250 J K –1 d. 105 J K –1 e. 930 J K –1 mol –1 7. What is true about the spontaneity of the decomposition of dichlorine heptoxide? 2 Cl 2 O 7 (g) 2 Cl 2 (g) + 7 O 2 (g) Δ H º = 135 kJ a. The decomposition is spontaneous at all temperatures. b. The decomposition is not spontaneous at any temperature. c. The decomposition is spontaneous at high temperatures. d. The decomposition is spontaneous at low temperatures. e. Not enough information is given to determine the spontaneity of this reaction. 8. Write a balanced reaction for which the following rate relationships are true. Rate =   25 NO 1 2t =   2 NO 1 4t =   2 O t a. 2 2 2 5 11 NO O N O 42  b. 2 5 2 2 N O NO 4 O 24  c. 2 5 2 2 2 N O 4 NO O d. 2 5 2 2 2 N O NO 4 O e. 2 2 2 5 4 NO 2 N O 9. For the net reaction, 2 NO ( g ) + O 2 ( g ) 2 NO 2 ( g ), which one of the following statements is most correct: a. If you double the concentration of NO you will double the rate of the reaction.
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CHEM1310F11_Final-Answers - CHEM 1310 Final Exam December...

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