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Exam Three-solutions

# Exam Three-solutions - Version 163 Exam Three cowley(89959...

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Version 163 – Exam Three – cowley – (89959) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points If a process is carried out at constant pressure P and the volume V of the system decreases, then Δ V is (negative, positive) and the work w is (negative, positive, zero). 1. positive; negative 2. negative; negative 3. negative; positive correct 4. negative; zero 5. positive; zero Explanation: Δ V = V f - V i < 0 since V i > V f . Thus w = - P Δ V > 0 since Δ V is negative. 002 10.0 points Cohesive forces are forces 1. between the molecules of the liquid and another surface. 2. Neither of these is correct. 3. between the molecules of a liquid. cor- rect Explanation: 003 10.0 points When a solution of ethanol (C 2 H 5 OH) is formed in water, the ethanol molecules 1. are attracted to the nonpolar water molecules. 2. form covalent bonds to the polar water molecules. 3. form hydrogen bonds to the polar water molecules. correct 4. are not attracted to the polar water molecules. Explanation: H C H H C H H O H O H H 004 10.0 points Heat flow is considered positive when heat flows (into, out of) a system; work is consid- ered positive when work is done (by, on) a system. 1. into; by 2. out of; on 3. out of; by 4. into; on correct Explanation: Heat flow q is considered positive when heat flows into a system. Work w is considered positive when work is done on a system. 005 10.0 points Which of these statements about thermody- namics is NOT TRUE? 1. Work done on the system is positive in sign. 2. Heat given o ff to the surroundings is neg- ative in sign. 3. Energy is conserved in chemical reac- tions. 4. The entropy of the system is always in- creasing. correct 5. Δ V , Δ S , and Δ H are examples of changes in thermodynamic state functions.

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Version 163 – Exam Three – cowley – (89959) 2 Explanation: The entropy of a system or its surroundings may increase or decrease. The Second Law of Thermodynamics states that in spontaneous changes, the universe tends toward a state of greater disorder; that is, entropy increases ( Δ S > 0). 006 10.0 points What is the molar mass of a 0.710 g sample of gas that occupies a volume of 0.600 L at a pressure of 0.776 atm and a temperature of 26.0 C?
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Exam Three-solutions - Version 163 Exam Three cowley(89959...

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