Question

Assertion :If both $\Delta H^0$ and $\Delta S^0$ are positive then reaction will be spontaneous at high temperature. Reason: All processes with positive entropy change are spontaneous.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is C Assertion is correct but Reason is incorrect

Spontaneity of a process depends upon $\Delta G^0$ which combines both factors $\Delta H^0$ and $\Delta S^0$.
$\Delta G^0=\Delta H^0-T\Delta S^0$
For spontaneity of a process, $\Delta G^0$ should be negative. If $\Delta H^0$ is +ve, $\Delta S^0$ is +ve then, $\Delta G^0$ will be -ve only when $T\Delta S>\Delta H$ which is possible only at high temperatures.