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HW 5 Thermodynamics I

# HW 5 Thermodynamics I - roberts(eer474 Homework 5...

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roberts (eer474) – 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. True correct 2. False 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. The energy of the products is higher than that of the reactants. 3. We can determine the absolute heat con- tent of the products and reactants. 4. Heat is evolved during the reaction. cor- rect 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. Δ E univ = 0 correct 2. Δ E univ < 0 3. Δ E sys = 0 4. Δ E univ > 0 5. Δ E sys < 0 6. Δ E sys > 0 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. lead 2. glass 3. copper 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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HW 5 Thermodynamics I - roberts(eer474 Homework 5...

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