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 $\Delta G,\,\,\Delta G$ 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.