CHM 132 - Exam 1 - 2003 Key

CHM 132 - Exam 1 - 2003 Key - Chemistry 132 Hour...

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Chemistry 132 Hour Examination 1 February 13, 2003 Name ( PRINT) __ SOLUTIONS ______________ Student number____________________________ Workshop Leader___________________________ There are four questions on this exam. You have up to 90 minutes to work this exam. Please be sure that you have a complete exam package. Please work exam problems on the pages provided. Show your work neatly and circle your answers. Give units for all answers requiring them. If you need additional space to complete a problem, please tell us where to look for your solution. Total (100 points) Score 1. (30 points)_____________ 2. (25 points)_____________ 3. (20 points)_____________ 4. (25 points)_____________
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SOLUTIONS _______________ 1. (30 points) Oxidation of fatty acids in tissues provides the heat required to sustain animals that hibernate, for example, polar bears. A particular such substance is arachidonic acid, C 20 H 32 O 2 . A 1.00 g sample of arachidonic acid is observed to liberate 42.0 kJ in its oxidation to CO 2 and H 2 O. (a) (6 points) Write the balanced chemical reaction corresponding to this oxidation process. C 20 H 32 O 2 + 27 O 2 20 CO 2 (g) + 16 H 2 O (l) (b) (12 points) 70% of the reaction enthalpy change is available to raise the bear’s temperature. Calculate the mass of arachidonic acid that must undergo oxidation in order to warm a 500 kg bear from 5 ° C to 15 ° C, assuming that the specific heat of bear tissue is 4.18 J g -1 K -1 . Heat absorbed by bear = (500 X 10 3 g)(4.18 J g -1 K -1 )(10 K) = 2.09 X 10 7 J = 2.09 X 10 4 kJ Let M = mass of acid: then 0.70 X M X 42 kJ = 2.09 X 10 4 kJ M = 2.09 X 10 4 /(42)(0.70) g = 710 g (c) (12 points) 15% of the reaction’s enthalpy is available to the bear for motion. Calculate the height in meters to which a bear could climb from the energy gained by the mass of arachidonic acid determined in part (b). 0.15 X 710 g X 42000 J g
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This test prep was uploaded on 04/17/2008 for the course CHM 132 taught by Professor Farrar during the Spring '08 term at Rochester.

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CHM 132 - Exam 1 - 2003 Key - Chemistry 132 Hour...

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