Test 4 - Version 450 Exam 4 McCord (53130) This print-out...

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Version 450 – Exam 4 – McCord – (53130) 1 This print-out should have 27 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. McCord CH301tt This exam is only For McCord’s Tues/Thur CH301 class. PLEASE carefully bubble in your UTEID and Version Number! You’ll need some (not all) oF the values From this table on the exam. Δ H f Δ G f S Substance ( J mol · K ) ( kJ mol ) ( kJ mol ) CaCO 3 (s) - 1206 . 9 - 1128 . 8 92.9 CaO(s) - 635 . 09 - 604 . 03 39.75 CO 2 (g) - 393 . 51 - 394 . 36 213.74 H 2 O(l) - 285 . 83 - 237 . 13 69.91 H 2 O(g) - 241 . 82 - 228 . 57 188.83 CH 4 (g) - 74 . 81 - 50 . 72 186.26 C 2 H 4 (g) +52 . 26 +68 . 12 219.56 C 3 H 8 (g) - 103 . 85 - 23 . 49 270.2 C 4 H 10 (g) - 126 . 15 - 17 . 03 310.1 C 6 H 6 ( ) +49 . 0 +124 . 5 173.3 C 8 H 18 ( ) - 249 . 9 +6 . 4 358 C 6 H 12 O 6 (s) - 1268 - 910 212 001 10.0 points The internal energy oF a substance can be brought to zero by cooling the substance all the way down to absolute zero ( T = 0 K). 1. True 2. ±alse correct Explanation: The very Fact that you have any matter at all means you have some internal energy - even at absolute zero. 002 10.0 points The process oF water Freezing to Form ice at 0 C is 1. an exothermic phase change. correct 2. neither exothermic nor endothermic. 3. an endothermic chemical reaction. 4. an endothermic phase change. 5. an exothermic chemical reaction. Explanation: Heat must be removed From the water For it to Freeze. This is exothermic. 003 10.0 points Two iron blocks oF equal mass are brought into thermal contact. Each block has a heat capacity oF 1000 J K 1 . One block is initially at a temperature oF 25 C the other is at 75 C. AFter they come to thermal equilibrium what is the total change in entropy For the two blocks combined? 1. Δ S = - 3 . 00 J K 1 2. Δ S = +2500 J K 1 3. Δ S = 0 . 00 J K 1 4. Δ S = - 2500 J K 1 5. Δ S = +6 . 00 J K 1 correct Explanation: Because the blocks have the same heat ca- pacity, the fnal temperature will simply be the average oF the temperature oF the two block which is 50 C. The total change in en- tropy will be the change in entropy For both blocks added together. The equation For en- tropy change For both blocks is C ln 323 . 15 298 . 15 + C ln 323 . 15 348 . 15 = 6 . 00 J K 1 004 10.0 points ±or the methanol combustion reaction 2 CH 3 OH( ) + 3 O 2 (g) -→ 2 CO 2 (g) + 4 H 2 O(g)
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Version 450 – Exam 4 – McCord – (53130) 2 estimate the amount of work done and tell whether the work was done on or by the sys- tem. Assume a temperature of 27 C. 1. 7.5 kJ, work done by the system correct 2. No work is done in this reaction. 3.
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Test 4 - Version 450 Exam 4 McCord (53130) This print-out...

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