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Unformatted text preview: Moore, Robert Homework 1 Due: Jan 26 2007, midnight Inst: McCord 1 This print-out should have 14 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. The due time is Central time. This homework has some Chapter 7 ques- tions and then gets into Chapter 8. You should recognize the first question as an isothermal expansion which is discussed in both Chapter 6 and in Chapter 7. 001 (part 1 of 1) 10 points Calculate G for the process He(g , 1 atm , 298 K) He(g, 10 atm, 298 K) 1. 5.70 kJ/mol correct 2. 3.50 kJ/mol 3. 3.90 kJ/mol 4. 4.80 kJ/mol 5. 2.10 kJ/mol Explanation: 002 (part 1 of 1) 10 points A reversible reaction is at equilibrium at con- stant pressure and temperature if the free energy of the system 1. is a maximum. 2. increases. 3. is a minimum. correct 4. is zero. 5. decreases. Explanation: A system is at equilibrium when G = 0. A system is spontaneous when G is negative and non-spontaneous when G is positive. Call Gibbs Free Energy at equilibrium G equil . If the system moves towards spontane- ity, G equil < G spont for G to be negative. Threfore, G equil must be a minimum. 003 (part 1 of 1) 10 points A reaction for which H is positive and S is negative 1. is spontaneous at any temperature. 2. could become spontaneous at high tem- peratures. 3. is not spontaneous at any temperature. correct 4. could become spontaneous at low temper- atures. Explanation: T = (+) , H = (+) and S = (- ) G = H- T S G = (+)- (+)(- ) = (+)- (- ) = (+) + (+) G will always be positive, so the process will always be nonspontaneous. 004 (part 1 of 1) 10 points Liquid metallic zinc (Zn) has a vapor pressure of 40 torr at 673 C and 100 torr at 736 C....
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This note was uploaded on 09/28/2009 for the course GE 206E taught by Professor staff during the Spring '09 term at University of Texas at Austin.
- Spring '09