115b07_Exam3key1_rec

115b07_Exam3key1_rec - Chem 115b Spring 2007 Exam 3 March...

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Chem 115b KEY Spring 2007 Print Name: Last First Exam 3 Last 3 digits of Student ID # March 8, 2007 TA's Name P r o f e s s o r R e i s l e r M a j o r Questions Points Score Grader 1 16 2 22 3 14 4 14 5 18 6 16 Total 100 INSTRUCTIONS 1. YOU MUST SHOW YOUR WORK TO RECEIVE CREDIT. 2. If necessary, please continue your solutions on the back of the preceding page (facing you). 3. YOU MUST USE BLACK INK TO BE ABLE TO REQUEST A REGRADE 4. Please read each question carefully before you write your answer. 5. There are 6 questions on 6 pages. ± Please Sign Below: I certify that I have observed all the rules of Academic Integrity while taking this examination. Signature:
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1 1. (16 pts) (A) (4 pts) Which of the following solutions will be the best buffer at a pH of 9.26? ( K a for HC 2 H 3 O 2 is 1.8 x 10 -5 , K b for NH 3 is 1.8 x 10 -5 ). a) 0.10 M HC 2 H 3 O 2 and 0.10 M Na C 2 H 3 O 2 b) 5.0 M HC 2 H 3 O 2 and 5.0 M Na C 2 H 3 O 2 c) 0.10 M NH 3 and 0.10 M NH 4 Cl d) 5.0 M NH 3 and 5.0 M NH 4 Cl e) 5.0 M HC 2 H 3 O 2 and 5.0 M NH 3 Answer: ____d_________ (B) (3 pts) The K sp of silver acetate (Ag C 2 H 3 O 2 ) is 1.9 x 10 -3 . You have a saturated solution in equilibrium with the solid salt. The effect on the solubility of adding to the solution either the acid HNO 3 or the base NH 3 will be: a) Either substance will decrease the solubility b) Either substance will increase the solubility c) NH 3 will increase the solubility; HNO 3 will decrease it. d) NH 3 will decrease the solubility; HNO 3 will increase it. e) NH 3 will decrease the solubility; HNO 3 will have no effect.
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This note was uploaded on 07/22/2008 for the course CHEM 115b taught by Professor Reisler during the Spring '08 term at USC.

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115b07_Exam3key1_rec - Chem 115b Spring 2007 Exam 3 March...

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