ex1s10 - NAME: KEY LARGO CHEMISTRY 419, SPRING, 2010 (2103)...

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NAME: KEY LARGO CHEMISTRY 419, SPRING, 2010 (2103) Examination 1, March 11, 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) From the diffusion coefficient of ribonuclease, (a) determine how far a ribonuclease particle moves in one second, if it is trapped in a very small (molecular-sized) pore so that it can only move in one dimension. According to the Handbook, the diffusion coefficient of ribonuclease is 11.9 10 -11 m 2 s -1 . One may use this value in the equation Dt x 2 This gives the following result: microns m s s m x 4 . 15 10 54 . 1 1 10 9 . 11 2 5 1 2 11 (b) Now, consider the movement of a ribonuclease particle in a three-dimensional fluid (the usual case). How far would it travel, on average, in that solution in one second? This is somewhat tricky. One has to realize that the square of the distance in three dimensions is x 2 + y 2 + z 2 . Each of these contributes 2Dt to the square of the distance, so that the total is 6Dt . The distance traveled is the square root of that number: microns m s s m Dt r 7 . 26 10 67 . 2 1 10 9 . 11 6 6 5 1 2 9 DO NOT WRITE IN THIS SPACE # 1________/10 # 2________/15 # 3________/20 # 4________/10 # 5________/15 # 6________/15 # 7________/15 ============= TOTAL PTS /100
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Score for Page NAME: CHEM 419, Exam 1, Spring, 2010, page 2 2. (15 points) Lysozyme was centrifuged at 55, 000 min -1 in water at 20 C. The following data were obtained. What is the sedimentation coefficient of lysozyme in water under these conditions? (Be sure to show all work clearly. HINT: A plot of appropriate functions may be helpful.) X b Time (min) (cm) X b /X b (0) ln(Xb/Xb(0) ) 0 6 1 0 30 6.07 1.01166 7 0.0115991 60 6.14 1.02333 3 0.0230653 90 6.21 1.035 0.0344014 120 6.28 1.04666 7 0.0456105 150 6.35 1.05833 3 0.0566953 This is Example Problem 24.11 in your text. A plot of the logarithm of the position of the boundary versus time should be linear, with the slope being s 2 . The graph below shows that it is linear.
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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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ex1s10 - NAME: KEY LARGO CHEMISTRY 419, SPRING, 2010 (2103)...

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