Question

A reaction occurs spontaneously if

• A. $T\Delta S < \Delta H$ and both $\Delta H$ and $\Delta S$ are + ve
• B. $T\Delta S > \Delta H$ and both $\Delta H$ and $\Delta S$ are + ve
• C. $T\Delta S = \Delta H$ and both $\Delta H$ and $\Delta S$ are + ve
• D. $T\Delta S > \Delta H$ and $\Delta H$ is + ve and $\Delta S$ is - ve

Answer 1

Answer: (B)

$T\Delta S > \Delta H$ and both $\Delta H$ and $\Delta S$ are + ve

Answer 2

The spontaneity of reaction is based upon the negative value of $1 G . \Delta G$ is based upon $T, \Delta S$ and $\Delta H$ according to following equation (Gibbs-Helmholtz equation) $\Delta G=\Delta H-T \Delta S$ If the magnitude of $\Delta H-T \Delta S$ is negative, then the reaction is spontaneous. when $T \Delta S>\Delta H$ and $\Delta H$ and $\Delta S$ are +ve, then $\Delta G$ is negative.