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Unformatted text preview: marquez (ecm739) H13: extra edition McCord (53110) 1 This print-out should have 5 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points This is an extra homework to bring our total to 13. This means you get to drop your 3 lowest homework scores and average your 10 others. This homework is really just some questions off of H11 and H12 (or just like them). Be careful, only 5 questions here (20 points each). When 0 . 53 g of compound X is burned com- pletely in a bomb calorimeter containing 3000 g of water, a temperature rise of 0 . 375 C is observed. What is U rxn for the combustion of compound X? The hardware component of the calorimeter has a heat capacity of 3 . 6 kJ/ C. The specific heat of water is 4.184 J/g C, and the MW of X is 56.0 g/mol. Correct answer:- 639 . 985 kJ / mol. Explanation: m X = 0 . 53 g MW X = 56.0 g/mol m water = 3000 g T = 0 . 375 C C s = 4.184 J/g C HC = 3 . 6 kJ/ C q cal = q water + q hardware q cal = C s m water T + C hardware T Then divide the heat by the number of moles, which is mass/MW. Also remember that because the temperature increased in the calorimeter, the reaction must be exothermic and the value of q (and therefore E ) is neg- ative....
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This note was uploaded on 10/25/2010 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.
- Spring '07