Question

Assertion: In an isolated system the entropy increases.
Reason: The processes in an isolated system are adiabatic.
A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If the assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false

Answer 1

Correct Answer - B
The entropy change of the universe during reversible processes is zero. During an adiabatic process no heat flows. Thus, we see that the entropy change of a systen during a reversible, adiabatic process is zero. But note that boht qualifers are needed, the entropy of a non-isolated system change during a reversible process (and the entropy change of the surrounding will compensate), and an irreversible change to an isolated system will increase the entrophy. hence option (b) is true.