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Unformatted text preview: Version 241 Exam 4 Sutcliffe (52410) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. SPECIAL NOTE: DUE TO THE LOG- ARITHMIC NATURE OF SOME OFTHE EQUATIONS YOU MAY FIND IF YOU DO NOT USE THE EXACT CONVER- SION TO KELVIN YOUR VALUE MAY BE SLIGHTLY DIFFERENT TO THE AN- SWER. IT SHOULD BE VERY CLOSE. 001 10.0 points K sp for iron(III) iodate (Fe(IO 3 ) 3 ) is 1 . 10 14 . We mix two solutions, one containing Fe 3+ and one containing IO 3 . At the instant of mixing, [Fe 3+ ] = 10 4 M and [IO 3 ] = 10 5 M. Which of the following statements is true? 1. None of the statements is true. 2. No precipitate forms because Q sp is less than K sp . correct 3. No precipitate forms because Q sp is greater than K sp . 4. A precipitate forms because Q sp is greater than K sp . 5. A precipitate forms because Q sp is less than K sp . Explanation: 002 10.0 points NOTE: A strong complex is one in which ev- erything is very tightly bound together. An- other way to put this would be to say that K d for FeEDTA is VERY tiny. Fe(OH) 3 (s) is very insoluble in water ( K sp = 1 . 6 10 39 ; however, Fe 3+ forms a strong complex with EDTA (FeEDTA , K f = 1 . 3 10 25 ). For a solution which is at equilibrium and contains Fe(OH) 3 (s) precipi- tate, which of the following occurs if EDTA is added to the solution? 1. Nothing happens because K sp is much smaller than K f . 2. More Fe(OH) 3 (s) precipitates because [Fe 3+ ] decreases. 3. No more Fe(OH) 3 (s) dissolves, but Fe 3+ complexes with EDTA. 4. More Fe(OH) 3 (s) dissolves. correct Explanation: 003 10.0 points NOTE: Below is a typo. Cross it out. The CORRECT sentence should read: For the reaction A + B X + Y For the reaction X + Y Z + R which arrow represents the activation energy of the forward reaction? e f c d a b A+B X+Y Reaction progress Potentialenergy 1. f 2. d 3. c 4. b correct 5. e 6. a Explanation: The activation energy is represented by the vertical line from the H of the reactants to the apex of the curve. Version 241 Exam 4 Sutcliffe (52410) 2 004 10.0 points For the reaction 2 NO(g) + 2 H 2 (g) N 2 (g) + 2 H 2 O(g) the following data were collected. [NO(g)] [H 2 (g)] Rate, M/s 0.10 0.10 0.0050 0.10 0.20 0.010 0.10 0.30 0.015 0.20 0.10 0.020 0.20 0.20 0.040 What is the rate law for this reaction? 1. rate = k [H 2 ] [NO] 2 2. rate = k [H 2 ] 2 [NO] 3. None of these 4. rate = k [H 2 ] [NO] 5. rate = k [H 2 ] [NO] 6. rate = k [H 2 ] [NO] 2 correct Explanation: 005 10.0 points What is the cell potential of the following cell? Pt | Br (aq , . 2 M) | Br 2 ( ) || Au + (aq , . 7 M) | Au(s) Br 2 + 2 e 2 Br E red = +1 . 09 V Au + + e Au E red = +1 . 69 V 1. . 65 V 2. . 55 V correct 3. . 72 V 4. . 48 V 5. . 60 V Explanation: The reaction involving Br must be reversed (cathode reaction) and the reaction involving Au must be doubled in order to balance the...
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This note was uploaded on 05/17/2009 for the course CH 52410 taught by Professor Sutcliffe during the Spring '09 term at University of Texas at Austin.
- Spring '09