Question

A reaction occurs spontaneously if

• A. $T△S<△H$ and both $△H,△S$ are $+ve$
• B. $T△S<△H$ and $△H=+ve,△S=-ve$
• C. $T△S>△H$ and both $△H,△S$ are $+ve$
• D. $T△S=△H$ and both $△H,△S$ are $+ve$

Answer 1

The correct option is C $T△S>△H$ and both $△H,△S$ are $+ve$

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 (Gibb's-Helmholtz equation)
$△G=△H-T△S$
when $△G=-veor<0$ reaction is spontaneous.
When $△S=+ve,△H=+ve$
at high temperatures only, $T△S>△H\Rightarrow △G=-ve$
when entropy factor favours and energy factor do not favour then spontaneity depends upon the temperature means at high temperature, $T△S>△H,△G=-ve$ and reaction is feasible.