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Unformatted text preview: mao (tm23477) Homework 5: Thermodynamics I Shear (52375) 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A closed system can exchange energy with the surroundings. 1. False 2. True correct Explanation: A closed system cannot exchange matter with the surroundings; it can exchange en- ergy. 002 10.0 points Which of the following statements is true about an exothermic reaction? 1. The change in enthalpy is positive. 2. Heat is evolved during the reaction. cor- rect 3. The energy of the products is higher than that of the reactants. 4. We can determine the absolute heat con- tent of the products and reactants. Explanation: Exothermic reactions release energy from the system into the surroundings. 003 10.0 points What is true about the first law of thermody- namics? 1. E univ = 0 correct 2. E univ < 3. E sys > 4. E sys < 5. E sys = 0 6. E univ > Explanation: 004 10.0 points Consider the following specific heats: copper, 0.384 J/g C; lead, 0.159 J/g C; water, 4.18 J/g C; glass, 0.502 J/g C. Which substance, once warmed, would be more likely to main- tain its heat and keep you warm through a long football game on a cold night? 1. copper 2. glass 3. lead 4. water correct Explanation: Water has the highest specific heat of the substances listed, so it has the capacity to emit the largest quantity of heat with minimal temperature loss; the emitted heat keeps you warm. The substance continues to warm you until its temperature is at or below your body temperature....
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- Spring '08