A gas is confined in a piston-cylinder device. The process is described as reversible. Which of the following HAS to be true?
A. The change in entropy of the gas is zero.
B. The change in entropy of the surroundings is zero.
C. The change in entropy of the universe is zero.
D. All of the above.
E. None of the above.
A. Incorrect. We do not know that the system is constant T, P or V, so entropy of the gas might change. Refer to Equation 4.54 to see this mathematically.
B. Incorrect. The gas could be reversibly compressed, losing heat to the surroundings, decreasing its entropy while increasing the surroundings’. Recollect that “the surroundings” are not the same as “the universe”. The universe is the surroundings AND the system.
C. Correct. A reversible process loses no possibility for obtaining work from the system, so Sgen = 0.
D. Incorrect. At least one of the statements is false.
E. Incorrect. At least one of the statements is true.
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