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Unformatted text preview: Chem 1B Name Exam 1B September 13, 2010 Instructions: For all mathematical problems, show your work. Give the basic formula (if there is one), rearrange it if necessary, plug in data with units, round properly to the correct number of significant figures, and place a box around the answer. For essay questions, be complete, but concise. Complete sentences with proper spelling and punctuation are expected. Useful information: R = 8.314 J/mol . K ln[A] t = -kt + ln[A] o 1 [A] t = kt + 1 [A] o [A] t = -kt + [A] o ln(k) = - E a R 1 T + ln(A) ln k 1 k 2 = E a R 1 T 2- 1 T 1 ln P 1 P 2 = H vap R 1 T 2- 1 T 1 For questions 1-12, choose the one best answer for each. 1. (2 pts.) For which one of the following reactions does the entropy of the system INCREASE? (a) NH 3 (g) + HCl(g) NH 4 Cl(s) (b) 2H 2 O 2 ( l ) 2H 2 O( l ) + O 2 (g) (c) NH 3 (g) + H 2 O( l ) NH 4 1+ (aq) + OH 1- (aq) (d) 2H 2 (g) + O 2 (g) 2H 2 O(g) (e) Ag 1+ (aq) + Cl 1- (aq) AgCl(s) 2. (2 pts.) Consider the following information: ice has a more ordered structure than liquid water and liquid water freezes spontaneously at -5 o C and 1 atm. Which of the following statements is most likely TRUE ? (a) Liquid water freezes at -5 o C because the endothermicity overcomes the decrease in entropy. (b) Liquid water freezes at -5 o C because the exothermicity overcomes the increase in entropy. (c) Liquid water freezes at -5 o C because the exothermicity overcomes the decrease in entropy. (d) Liquid water freezes at -5 o C because the increase in entropy overcomes the endothermicity. (e) None of these statements is TRUE . 3. (2 pts.) For a certain process, S surr > 0. The process: (a) is at equilibrium. (b) is endothermic. (c) decreases the entropy of the universe. (d) is exothermic. (e) is spontaneous. 4. (2 pts.) Which of the following statements is TRUE ? (a) An exothermic process that is accompanied by an increase in the entropy of the system will always be spontaneous. (b) A process in which the entropy of the surroundings increases will always be spontaneous. (c) An endothermic process can never be spontaneous. (d) A process in which the entropy of the system increases will always be spontaneous. (e) An exothermic process will always be spontaneous. 5. (2 pts.) All of the gas-phase reactions listed below are endothermic. Which one of these reactions is most likely to be non-spontaneous at ALL temperatures? (a) 4NO(g) + 6H 2 O(g) 4NH 3 (g) + 5O 2 (g) (b) CH 3 OH(g) CO(g) + 2H 2 (g) (c) N 2 O 4 (g) 2NO 2 (g) (d) 2SO 3 (g) 2SO 2 (g) + O 2 (g) (e) COCl 2 (g) CO(g) + Cl 2 (g) 6. (2 pts.) Consider the following characteristics of chemical reactions, I. spontaneity II. maximum amount of work that can be done III. speed The value of G for a chemical reaction under a given set of conditions provides information about: (a) I, II and III...
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This note was uploaded on 12/21/2010 for the course CHEM 1B taught by Professor Garyj.decicco during the Fall '10 term at Santa Rosa.
- Fall '10