# ch20 - Chapter 20 ENTROPY AND THE SECOND LAW OF...

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Chapter 20: ENTROPY AND THE SECOND LAW OF THERMODYNAMICS 1. In a reversible process the system: A. is always close to equilibrium states B. is close to equilibrium states only at the beginning and end C. might never be close to any equilibrium state D. is close to equilibrium states throughout, except at the beginning and end E. is none of the above ans: A 2. A slow (quasi-static) process is NOT reversible if: A. the temperature changes B. energy is absorbed or emitted as heat C. work is done on the system D. friction is present E. the pressure changes ans: D 3. The di f erence in entropy S = S B S A for two states A and B of a system can be computed as the integral \$ dQ/T provided: A. A and B are on the same adiabat B. A and B have the same temperature C. a reversible path is used for the integral D. the change in internal energy is f rst computed E. the energy absorbed as heat by the system is f rst computed ans: C 4. Possible units of entropy are: A. J B. J/K C. J 1 D. liter · atm E. cal/mol ans: B 5. Which of the following is NOT a state variable? A. Work B. Internal energy C. Entropy D. Temperature E. Pressure ans: A 308 Chapter 20: ENTROPY AND THE SECOND LAW OF THERMODYNAMICS

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6. The change in entropy is zero for: A. reversible adiabatic processes B. reversible isothermal processes C. reversible processes during which no work is done D. reversible isobaric processes E. all adiabatic processes ans: A 7. Which of the following processes leads to a change in entropy of zero for the system undergoing the process? A. Non-cyclic isobaric (constant pressure) B. Non-cyclic isochoric (constant volume) C. Non-cyclic isothermal (constant temperature) D. Any closed cycle E. None of these ans: D 8. Rank, from smallest to largest, the changes in entropy of a pan of water on a hot plate, as the temperature of the water 1. goes from 20 Cto30 C 2. goes from 30 Cto40 C 3. goes from 40 Cto45 C 4. goes from 80 Cto85 C A. 1, 2, 3, 4 B. 4, 3, 2, 1 C. 1 and 2 tie, then 3 and 4 tie D. 3 and 4 tie, then 1 and 2 tie E. 4, 3, 2, 1 ans: E 9. An ideal gas expands into a vacuum in a rigid vessel. As a result there is: A. a change in entropy D. an increase of pressure B. a change in temperature E. a decrease of internal energy C. a change in phase ans: A 10. Consider all possible isothermal contractions of an ideal gas. The change in entropy of the gas: A. is zero for all of them B. does not decrease for any of them C. does not increase for any of them D. increases for all of them E. decreases for all of them ans: E Chapter 20: ENTROPY AND THE SECOND LAW OF THERMODYNAMICS 309
11. An ideal gas is to taken reversibly from state i, at temperature T 1 , to any of the other states labeled I, II, III, IV, and V on the p - V diagram below. All are at the same temperature T 2 . Rank the

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ch20 - Chapter 20 ENTROPY AND THE SECOND LAW OF...

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