Homework 09 - Su, Yung Homework 9 Due: Dec 2 2007, 11:00 pm...

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Unformatted text preview: Su, Yung Homework 9 Due: Dec 2 2007, 11:00 pm Inst: FAKHREDDINE 1 This print-out should have 40 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. The due time is Central time. Each question is worth one point. 001 (part 1 of 1) 1 points Which of the following is true of a general thermodynamic state function? 1. The value of the state function remains constant. 2. The value of a state function does NOT change with a change in temperature of a process. 3. The change in the value of a state func- tion is always negative for a spontaneous re- action. 4. The change in the value of the state func- tion is always positive for endothermic pro- cesses. 5. The change of the value of a state func- tion is independent of the path of a process. correct Explanation: A change in a state function describes a difference between the two states. It is inde- pendent of the process or pathway by which the change occurs. 002 (part 1 of 1) 1 points In thermodynamics, when energy changes oc- cur during a process, we put the changes into two categories: 1. Joules and kiloJoules. 2. potential and kinetic energy. 3. enthalpy and internal energy. 4. heat and work. correct 5. external and internal energy. Explanation: All the energy contained within a sub- stance is E , the internal energy. These en- ergy changes are either heat ( q ) or work ( w ) changes. E = E f- E i = q + w 003 (part 1 of 1) 1 points If a system absorbs heat and also does work on its surroundings, its energy 1. must decrease. 2. may either increase or decrease, depend- ing on the relative amounts of heat absorbed and work done. correct 3. must increase. 4. must not change. Explanation: E = q + w q > 0 because heat is absorbed and w < 0 be- cause the system does work on its surround- ings. Therefore E = (+) + (- ). E can be positive only if q > w , and negative only if w > q . 004 (part 1 of 1) 1 points The standard molar heat of fusion of ice is 6020 J/mol. Calculate q , w , and E for melting 1.00 mol of ice at 0 C and 1.00 atm pressure. 1. q = 6020 J/mol, w =- 6020 J/mol, and E = 0 2. q = 6020 J/mol, w = 0, and E = 6020 J/mol correct 3. q = 6020 J/mol, w = 6020 J/mol, and E = 12040 J/mol 4. q =- 6020 J/mol, w = 6020 J/mol, and E = 0 Su, Yung Homework 9 Due: Dec 2 2007, 11:00 pm Inst: FAKHREDDINE 2 5. q =- 6020 J/mol, w = 0, and E =- 6020 J/mol Explanation: E = q + w q = H w =- P V =- ( n ) R T Since the water is never in the gas phase, V 0, so w = 0 and H = E . Melting requires energy absorption by the system, so it is endothermic and H is positive. 005 (part 1 of 1) 1 points A sample of an ideal gas having a volume of 0.701 L at 298 K and 10.0 atm pressure is al- lowed to expand against a constant opposing pressure of 0.541 atm until it has a volume of 1.000 L at 200 K and the pressure equals the opposing pressure. What is the work for the system?...
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This note was uploaded on 04/15/2009 for the course CH 54740 taught by Professor Fakhreddine during the Spring '09 term at University of Texas at Austin.

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Homework 09 - Su, Yung Homework 9 Due: Dec 2 2007, 11:00 pm...

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