Exam3_key_W09 - Name: KEY Chem 230 Exam #3 April 7, 2009...

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Name: KEY Chem 230 Exam #3 April 7, 2009 Discussion Section #: INSTRUCTIONS: Use only the space provided to answer the questions. If you need more work space, start your answer on the back of a page and then write only your final answer in the space provided. Anything written in the margins and on the back of pages will not be graded. Make sure your final answer is clearly marked . Multiple choice: Mark all multiple choice clearly, by both circling the correct choice and writing the letter. Each multiple choice question is worth 3 points. Short answer: Most questions can be answered solely with numbers, equations/expressions, or short phrases. When asked to "explain" or "justify," use a maximum of two sentences or an annotated equation. If the question does not ask you to "explain" or "justify," you do not need to do so. Inclusion of excessive incorrect information may lead to point deductions, even in otherwise correct answers. Provide units for all final numerical answers, if any. Showing clear work within the space provided is recommended for calculations to allow for partial credit. When provided, all final answers should be placed in the box provided for the question. Short answer questions are worth the number of points indicated on the problem. The exam totals to 150 points. A periodic table is attached as the last page of the exam. Please turn in the table with the exam if you tear it off. Use F = 10 5 C mol -1 where needed
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Name: KEY 1) Given the reduction potentials below, what is for Hg 2+ (aq) + 2 e - → Hg( l )? Hg 2+ (aq) + e - → Hg + (aq) has = 1.3 V Hg + (aq) + e - → Hg( l ) has = 0.3 V a) 1.6 V b) 1.0 V *c) 0.8 V d) -1.0 V e) None of the above 3 = n 1 1 + n 2 2 / n 3 = (1)(1.3)+(1)(0.3)/(2) 2) The maximum possible amount of work a redox system can perform ( w elec ) is equal to what? *a) Δ G b) Δ c) Δ E d) Δ e) All of the above f) None of the above Work is general, not limited to standard conditions, and is energy, not potential 3) For the galvanic cell Co(s) | Co 2+ (aq) || Au 3+ (aq) | Au(s) with the reduction potentials below, which of the following ions is a good salt bridge choice? Co 2+ (aq) | Co(s) has = -0.3 V Au 3+ (aq) | Au(s) has = 1.4 V a) Mn 3+ , where Mn 3+ (aq) | Mn 2+ (aq) has = 1.5 V Au side, so 1.5 - 1.4 = 0.1 V, bad b) NO 3 - , where NO 3 - (aq) | NO 2 - (aq) has = 0.0 V Co side, so 0 - -0.3 = 0.3 V, bad *c) SO 4 2- , where SO 4 2- (aq) | SO 3 2- (aq) has = -0.9 V Co side, so -0.9 - -0.3 = -0.6 V d) All of the above are good choices e) None of the above are good choices 4) Which of the following is a true statement about the Li-ion battery based on the electrochemical cell Li 2 FeSiO 4 (s) | LiFeSiO 4 (s) || C(s) | LiC 6 (s), if Si is +4 at all times? a)
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Exam3_key_W09 - Name: KEY Chem 230 Exam #3 April 7, 2009...

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