fes10 - NAME KEY FRANCIS SCOTT CHEMISTRY 419 SPRING...

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NAME: KEY, FRANCIS SCOTT CHEMISTRY 419, SPRING, 2010 (2103) Final Examination, May 22, 2010 Answer each question in the space provided; use back of page if extra space is needed. Answer questions so the grader can READILY understand your work; only work on the exam sheet will be considered. Write answers, where appropriate, with reasonable numbers of significant figures. You may use only the "Student Handbook," a calculator, and a straight edge . 1. (10 points) The diffusion coefficient of lysozyme (MW = 14.1 kg/mol is 0.104 10 -9 m 2 s -1 . How long does it take this protein, on average, to diffuse an rms distance of exactly 1 m in solution? The root-mean-square distance traveled in three-dimensional diffusion is Dt r 6 2 Substitution into this equation gives the result: ms s s m m D r t 6 . 1 10 60 . 1 10 104 . 0 6 ) 10 1 ( 6 3 1 2 9 2 6 2 DO NOT WRITE IN THIS SPACE # 1________/10 # 2________/10 # 3________/10 # 4________/10 # 5________/10 # 6________/10 #7 ________/10 #8 ________/10 #9 ________/10 #10 _______/10 #11 _______/10 ============= Extra credit #12 _______/10 ============= TOTAL PTS /110 ============= PERCENTAGE
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Score for Page NAME: CHEM 419, Final Exam, Spring, 2010, page 2 2. (10 points) Iodine reacts with a ketone in aqueous solution to form an iodoketone by the following reaction: H I iodoketone ketone I 2 Birk and Walters ( J. Chem. Ed ., 69 , 585 – 587 (1992)) report the following initial-rate data for the iodination of acetone measured at 23 C. [Acetone] (mol dm -3 ) [H + ] (mol dm -3 ) [I 2 ] (mol dm -3 ) 10 6 Initial rate (mol dm -3 s -1 ) 1.33 0.0404 0.00665 1.85 1.33 0.0809 0.00665 3.89 0.333 0.323 0.00665 3.76 0.667 0.323 0.00665 7.55 0.333 0.323 0.00332 3.75 Write the rate law for this reaction, showing the orders with respect to the reactants and the hydrogen ion. Show your work and explain how you got the answers. [HINT: Remember that orders are generally whole numbers (or perhaps half order). So, a slight difference from integral orders may be considered to be due to experimental error.] The various orders are found by taking the appropriate ratios. For example, since the iodine and acetone are constant in the first two experiments, it can be used to determine the dependence on hydrogen ion concentration: 89 . 3 85 . 1 0809 . 0 404 . 0 n Taking the logarithm of both sides gives the following equation: 74322 . 0 69438 . 0 n Solving this for n gives: 07 . 1 69438 . 0 74322 . 0 n , which is close to 1. Similarly one may use the third and fourth experiments to determine the order with respect to acetone. 55
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This note was uploaded on 02/02/2012 for the course CHEM 419 taught by Professor Staff during the Fall '10 term at University of Delaware.

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fes10 - NAME KEY FRANCIS SCOTT CHEMISTRY 419 SPRING...

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