Question

Assertion : If both $\Delta H^{\circ }$ and $\Delta S^{\circ }$ are positive then reaction will be spontaneous at high temperature.
Reason : All processes with positive entropy change are spontaneous.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both 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

Answer: (C)

Spontaneity of a process depends upon $\Delta G^{\circ }$ which combines both factors $\Delta H^{\circ }$ and $\Delta S^{\circ }$.
$\Delta G^{\circ }=\Delta H^{\circ }-T\Delta S^{\circ }$
For the spontaneity, $\Delta G^{\circ }$ should be negative. If $\Delta H^{\circ }$ is $+ve$, $\Delta S^{\circ }$ is $+ve$ then, $\Delta G^{\circ }$ to be $-ve$ only when $T\Delta S>\Delta H$ which is possible at high temperature.