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Exam04answers 2011 pg1

Exam04answers 2011 pg1 - This print-out should have 20...

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This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. C 6 H 5 COOH = 122.1 g/mol (benzoic acid) C 3 H 8 = 44.1 g/mol (propane) ozone is O 3 001 (part 1 of 1) 10 points What mass of propane (C 3 H 8 (g)) must be burned to supply 2775 kJ of heat? The stan- dard enthalpy of combustion of propane at 298 K is - 2220 kJ · mol - 1 . 1. 44.1 g 2. 102 g 3. 35.3 g 4. 55.1 g correct 5. 75.9 g Explanation: 2775 / 2220 = 1.25 mol of propane 1.25 mol × 44.1 g/mol = 55.1 g of propane 002 (part 1 of 1) 12 points The temperature of 2.00 mol CO 2 (g) is in- creased from 10 C to 150 C at constant pres- sure. Calculate the change in the entropy of carbon dioxide. Assume ideal behavior. 1. +17 . 71 J/K 2. - 11 . 70 J/K 3. +11 . 70 J/K 4. - 23 . 30 J/K T 1 = 10 C = 283 K T 2 = 150 C = 423 K n = 2 mol C p , m = 8 . 314 J mol · K Δ S = nC p , m ln parenleftbigg T 2 T 1 parenrightbigg = (2 mol) 7 2 ( 8 . 314 J mol · K ) × ln parenleftbigg 423 K 283 K parenrightbigg = 23 . 3912 J / K 003 (part 1 of 1) 10 points Air is cooled until it freezes and the solid air is cooled to nearly 0 K. What value does the en- tropy of the resulting solid mixture approach
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