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Which combination of the following statements is correct?
P: A gas cools upon expansion only when its Joule-Thomson coefficient is positive in the temperature range of expansion.
Q: For a system undergoing a process, its entropy remains constant only when the process is reversible.
R: The work done by a closed system in an adiabatic is a point function.
S: A liquid expands upon freezing when the slope of its fusion curve on pressureTemperature diagram is negative.
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- R and S
- P and Q
- Q, R and S
- P, Q and R
Correct Option: A
First law of thermodymnamics,
1. δ Q = dU + δ W
Adiabatic, δ Q = 0
dU = – δ W
Hence work acts as the point function.
2. Liquid expands upon freezing when the liquid is water. In case of water the slope of fusion curve is negative.
