Ch 301 HW 10 - Homework 10 Sutcliffe (52380) 1 This...

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Unformatted text preview: 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 72.0 mmol of a perfect gas at 359 K, the volume of the gas is reduced to 18.0% of its initial value. Calculate w for this process. Correct answer: 368 . 5 kJ. Explanation: w =- nRT ln parenleftbigg V f V i parenrightbigg w =- (72 / 1000)8 . 314(359) ln(18 / 100) w = 368 . 5 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 fourth law 2. the first 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 does not apply to pho- tochemical reactions. 2. This reaction is characterized by an en- ergy change so close to zero that it is essen- tially reversible. 3. It is not a spontaneous chemical reaction; it is driven by an external agency light. correct 4. Thermodynamics deals only with closed systems; photosynthesis is an open system. 5. Thermodynamics does not apply to living systems. 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. 27 . 3 kJ/K 4. 34 . 0 J/K correct 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 Homework 10 Sutcliffe (52380) 2 005 10.0 points What is the change in entropy of the sys- tem for freezing 4 mol of CH 3 OH( ) at its normal freezing point? T f H fus T b H vap (K) (kJ/mol) (K) (kJ/mol) 175 . 2 3 . 16 337 . 8 35 . 3 Correct answer: 72 . 1461 J / K. Explanation: H fus = 3160 J / mol T = 175 . 2 K n = 4 mol S system = H system T = (4 mol)(3160 J / mol) 175 . 2 K = 72 . 1461 J / K 006 10.0 points Calculate the boiling point of a liquid for which H vap = 33 kJ / mol and S vap = 136 J / mol K....
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Ch 301 HW 10 - Homework 10 Sutcliffe (52380) 1 This...

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