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Unformatted text preview: padilla (tp5647) – HW13: Thermodynamics I – shear – (52375) 1 This print-out should have 22 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 On January 1, 2001, a bookstore had 266,478 books in stock. On February 1, 2001, the same bookstore had 257,814 books in stock. What is the value of Δ(books) for the bookstore during that period? Correct answer:- 8664 books. Explanation: B f = 257 , 814 books B i = 266 , 478 books Δ B = B f- B i = 257 , 814 books- 266 , 478 books =- 8664 books Thus the bookstore had 8664 fewer books on February 1. 003 10.0 points What is true about the first law of thermody- namics? 1. Δ E sys > 2. Δ E univ > 3. Δ E sys = 0 4. Δ E univ = 0 correct 5. Δ E univ < 6. Δ E sys < Explanation: 004 10.0 points A property that determines the direction of heat flow is 1. temperature. correct 2. combustion. 3. entropy. 4. calorie. Explanation: Heat flows spontaneously from a hotter body to a colder body. In other words, heat flows from a body of high temperature to a body of lower temperature. 005 10.0 points Which of the following statements is true about an exothermic reaction? 1. We can determine the absolute heat con- tent of the products and reactants. 2. The change in enthalpy is positive. 3. Heat is evolved during the reaction. cor- rect 4. The energy of the products is higher than that of the reactants. Explanation: Exothermic reactions release energy from the system into the surroundings. 006 10.0 points 3.5 g of a hydrocarbon fuel is burned in a ves- sel that contains 250. grams of water initially at 25.00 C. After the combustion, the temper- ature of the water is 26.55 C. How much heat is evolved per gram of fuel burned? 1. 73.5 J/g padilla (tp5647) – HW13: Thermodynamics I – shear – (52375) 2 2. 1263 J/g 3. 463 J/g correct 4. 143 J/g 5. 1105 J/g 6. 1764 J/g 7. 26555 J/g 8. 511 J/g Explanation: q = m Cp Δ T q = 250 (4.184) 1.55 = 1621.3 J per gram will be 1621.3 J / 3.5 g = 463 J/g 007 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. water correct 3. glass 4. copper 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 '09
- Enthalpy, kJ/mol, Padilla