Homework 10-solutions - dewitt (aad777) Homework 10...

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Unformatted text preview: dewitt (aad777) Homework 10 sutcliffe (52380) 1 This print-out should have 18 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. This is your LAST Homework!!! 001 10.0 points In the isothermal compression of 68.0 mmol of a perfect gas at 325 K, the volume of the gas is reduced to 19.0% of its initial value. Calculate w for this process. Correct answer: 305 . 1 kJ. Explanation: w =- nRT ln parenleftbigg V f V i parenrightbigg w =- (68 / 1000)8 . 314(325) ln(19 / 100) w = 305 . 1 kJ 002 10.0 points The fact that a heat pump requires energy to move heat from a colder object (the outside of a house) to a hotter object (the inside of the house) is a real life observation of which thermodynamic law? 1. the first law 2. the fourth law 3. the third law 4. the second law correct Explanation: The Second Law of Thermodynamics states that in spontaneous changes the universe tends toward a state of greater disorder. In other words, in spontaneous reactions S Univ > 0. Energy must be used to make the reaction spontaneous. 003 10.0 points The oxidation of sugar to carbon dioxide and water is a spontaneous chemical reac- tion. Since we know that reactions that occur spontaneously in one direction cannot occur spontaneously in the reverse direction, how can we understand photosynthesis? 1. Thermodynamics deals only with closed systems; photosynthesis is an open system. 2. It is not a spontaneous chemical reaction; it is driven by an external agency light. correct 3. Thermodynamics does not apply to pho- tochemical reactions. 4. Thermodynamics does not apply to living systems. 5. This reaction is characterized by an en- ergy change so close to zero that it is essen- tially reversible. Explanation: It is not a spontaneous chemical reaction; it is driven by an external agency light. 004 10.0 points Imagine that one carbon in buckminster- fullerene (C 60 ) is replaced by a silicon atom, yielding SiC 59 . This molecule can then orient in 60 different ways. What is the entropy of one mole of SiC 59 at T = 0 K? 1. 4 . 53 10 20 J/K 2. 5 . 65 10 23 J/K 3. 34 . 0 J/K correct 4. 27 . 3 kJ/K Explanation: n = 1 mol k = 1 . 38066 10 23 J / k W = 60 N A = 6 . 02214 10 23 mol 1 S = nk N A ln W = (1 mol)(1 . 38066 10 23 J / k) (6 . 02214 10 23 mol 1 ) ln(60) = 34 . 0425 J / K 005 10.0 points dewitt (aad777) Homework 10 sutcliffe (52380) 2 WITHDRAWN 006 10.0 points Calculate the boiling point of a liquid for which H vap = 20 kJ / mol and S vap = 140 J / mol K. Correct answer: 142 . 857 K. Explanation: H vap = 20 kJ / mol S vap = 140 J / mol K During phase changes G = 0 . Solve for T when G = 0: G = H- T S = 0 T = H S = 20 kJ / mol . 14 kJ / mol K = 142 . 857 K 007 10.0 points Consider the following processes. (Treat all gases as ideal.) I) The pressure of one mole of oxygen gas is allowed to double isothermally.is allowed to double isothermally....
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This note was uploaded on 10/20/2011 for the course CH 301 taught by Professor Fakhreddine/lyon during the Fall '07 term at University of Texas at Austin.

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Homework 10-solutions - dewitt (aad777) Homework 10...

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