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)

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.