hw11 - irshad(si2865 – HW11 – distler –(57205 1 This...

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Unformatted text preview: irshad (si2865) – HW11 – distler – (57205) 1 This print-out should have 23 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A cup of coffee (with a lid) is enclosed in an insulated cup 0 . 5 cm thick in the shape of a cube 14 . 3 cm on a side. The thermal con- ductivity of the cup is 0 . 0002 cal / s · cm · ◦ C. The temperature of the coffee is 93 ◦ C, and the temperature of the surroundings is 28 ◦ C. Find the heat loss due to conduction. Correct answer: 133 . 535 J / s. Explanation: Let : k = 0 . 0002 cal / s · cm · ◦ C , a = 14 . 3 cm , T 1 = 93 ◦ C , T 2 = 28 ◦ C , and L = 0 . 5 cm . The heat flow through a surface with the area A is H = k A Δ T L = k (6 a 2 ) Δ T L = (0 . 0002 cal / s · cm · ◦ C) × 6 (14 . 3 cm) 2 · 93 ◦ C- 28 ◦ C . 5 cm × 4 . 186 J cal = 133 . 535 J / s . 002 10.0 points If the gas in a container absorbs 275 Joules of heat, has 125 Joules of work done on it, then does 50 Joules of work, what is the increase in the internal energy of the gas? 1. Δ U = 200 J 2. Δ U = 400 J 3. Δ U = 350 J correct 4. Δ U = 100 J 5. Δ U = 450 J Explanation: Let : Δ Q = 212 J , W 1 = 100 J , and W 2 = 52 J . The total work done by the gas is Δ W = W 2- W 1 . Using the first law of thermodynamics, Δ U = Δ Q- Δ W = Δ Q- ( W 2- W 1 ) = 212 J- (52 J- 100 J) = 260 J . 003 10.0 points The internal energy of the gas in a gasoline engine’s cylinder decreases by 253 . 3 J. If 23.0 J of work is done by the gas, how much energy is transferred as heat? Correct answer:- 230 . 3 J. Explanation: Let : Δ U =- 253 . 3 J and W = 23 . 0 J . Δ U = Q- W Q = Δ U + W =- 253 . 3 J + 23 J =- 230 . 3 J . 004 10.0 points An ideal gas is initially in a state that corre- sponds to point 1 on the graph below, where it has pressure P 1 , volume V 1 , and temperature T 1 . The gas undergoes an isothermal process represented by the curve shown, which takes it to a final state 3 at temperature T 3 . irshad (si2865) – HW11 – distler – (57205) 2 V 1 P 1 O Pressure(Pacal) Volume (liter) Pressure vs Volume T 1 1 T 2 2 T 3 3 T 4 4 If T 2 and T 4 are the temperatures the gas would have at points 2 and 4, respectively, which of the following relationships is true?...
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This note was uploaded on 07/13/2011 for the course CHEM 301 taught by Professor Wandelt during the Spring '08 term at University of Texas.

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hw11 - irshad(si2865 – HW11 – distler –(57205 1 This...

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