MT2-Sp10-key

MT2-Sp10-key - Name_ GSI _ Chemistry 4B, Spring 2010 March...

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Name__________________ GSI ____________________ Page 1 of 7 Chemistry 4B, Spring 2010 March 12, 2010 (50 min., closed book) Name: KEY G S I : S I D : S e c t i o n : Write your name and that of your GSI on all 7 pages of the exam. Equations, constants, and data are provided on the second page of the exam. In order to maximize your score on the exam: Do the questions you know how to do first. Circle your final answer. Go back and spend more time on the questions you find more challenging. Budget your time carefully -- don't spend too much time on one problem. Show all work for which you want credit and don't forget to include units. For the explanation sections, try to keep your answers brief as well as complete. Question Topic Page Points Score 1 Rate Law 2 20 2 Arrhenius 3 20 3 Steady-State 4 24 4 Dynamics 5 24 5 Chromatography 6 12 Total 100 Useful Equations and Constants R = 8.314 J / (mol K) y mx b bc A G = RT ln K kt A A t 0 ] [ ] [ ln kt B B t 0 ] [ 1 ] [ 1 k Ae E a RT
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Name__________________ GSI ____________________ Page 2 of 7 Question 1) Experimental Determination of Rate Law Several experiments were performed to determine the rate law for the following reaction. BrO 3 - (aq) + 5Br - (aq) + 6H + (aq) 3Br 2 (aq) + 3H 2 O (l) Initial Concentration (mol/L) Experiment BrO 3 - Br - H + Rate = d[BrO 3 - ]/dt (mol /L· sec) 1 0.10 0.10 0.10 1.2 × 10 -3 2 0.20 0.10 0.10 2.4 × 10 -3 3 0.10 0.30 0.10 3.5 × 10 -3 4 0.10 0.10 0.20 4.8 × 10 -3 a) Find the order of the reaction with respect to each reactant. [BrO 3 - ] (0.10/0.20) x = (1.2 × 10 -3 /2.4 × 10 -3 ) x = 1 [Br - ] (0.10/0.30) y = (1.2 × 10 -3 /3.5 × 10 -3 ) y = 1 [H + ] (0.10/0.20) z = (1.2 × 10 -3 /4.8 × 10 -3 ) z = 2 b) Write the rate law for the reaction. d[BrO 3 - ]/dt = k[BrO 3 - ][Br - ][H + ] 2 c) From the data for experiment #4, determine the value of the rate constant. (Show units.) d[BrO 3 - ]/dt = k[BrO 3 - ][Br - ][H + ] 2 k(0.10 mol/L)(0.10 mol/L)(0.20 mol/L) 2 = 4.8 × 10 -3 mol /L· sec k = 12 L 3 mol -3 sec -1 4 /20 4 4 4 4
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Name__________________ GSI ____________________ Page 3 of 7 Question 2) Arrhenius Behavior of Gas Phase Reactions An Arrhenius plot is shown for the reaction of Br radicals with H 2 gas.
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MT2-Sp10-key - Name_ GSI _ Chemistry 4B, Spring 2010 March...

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