$\Delta$G = $\Delta$H – T$\Delta$S

For a reaction to become spontaneous, $\Delta$G must be negative.

For case (a) exothermic and increasing disorder

For exothermic reaction,

$\Delta$H = –ve and increasing disorder,

$\Delta$S = +ve

$\Delta$G = –ve –T(+ve)

Thus, $\Delta$G is negative for all temperature range

For case (b) exothermic and decreasing disorder For exothermic reaction, $\Delta$H = –ve and for decreasing disorder,

$\Delta$S = –ve

$\Rightarrow$ $\Delta$G = –ve – T(–ve)

Thus, $\Delta$G is not negative for all temperature range.

For case (c) endothermic and increasing disorder. For endothermic reaction, $\Delta$H = +ve and increasing disorder,

$\Delta$S = +ve

Thus, $\Delta$G is not negative for all temperature range.

For case (d) endothermic and decreasing disorder

For endothermic reaction,

$\Delta$H = +ve and decreasing disorder,

$\Delta$S = –ve

$\Delta$G = +ve – T (–ve)

Thus, $\Delta$G is positive for all temperature range.