Thermodynamics Multiple Choice Questions on “The Property of Entropy”.
1. Integral of dQ/T is independent of reversible path connecting between two points.
a) true
b) false
Answer: a
Clarification: For two reversible paths, dQ/T doesn’t depend on the path taken.
2. Integral of dQ/T of a reversible path is given by
a) Si-Sf
b) Sf-Si
c) Si+Sf
d) -Si-Sf
Answer: b
Clarification: Integral of dQ/T is = Sf-Si where i=initial equilibrium state and f=final equilibrium state.
3. Entropy is a
a) path function, intensive property
b) path function, extensive property
c) point function, intensive property
d) point function, extensive property
Answer: d
Clarification: Fact about entropy and unit of entropy is J/K.
4. Specific entropy is given by( where m is the mass)
a) Sm
b) m/S
c) S/m
d) none of the mentioned
Answer: c
Clarification: s=S/m with unit J/kg K.
5. For any process which is undergone by a system
a) dQ/T>=ds
b) dQ/T<=ds
c) dQ/T≠ds
d) none of the mentioned
Answer: b
Clarification: For any process dQ/T<=ds and this comes from Clausius theorem.
6. For a reversible process,
a) dS=dQ/T
b) dS>dQ/T
c) dS
Answer: a
Clarification: For a reversible process, dQ/T is equal to the net change in entropy.
7. For an irreversible process,
a) dS=dQ/T
b) dS>dQ/T
c) dS
Answer: b
Clarification: For a irreversible process, change in entropy is greater than dQ/T.
8. For two different paths between same two points, entropy change is
a) depends on path taken
b) different
c) same
d) none of the mentioned
Answer: c
Clarification: This is because entropy is a property.
9. For the general case, we can write
a) S2-S1<=dQ/T for a path
b) S2-S1>=dQ/T for a path
c) S2-S1≠dQ/T for a path
d) none of the mentioned
Answer: b
Clarification: The equality sign holds good for a reversible process and the inequality sign for an irreversible process.
10. When two equilibrium states are infinitesimally near,
a) dQ/T=dS
b) dQ/T>dS
c) dQ/T
Answer: a
Clarification: dS is an exact differential because S is a point function and a property.