Question

An exothermic reaction A→B is spontaneous in the backward direction. What will be the sign of DS for the forward reaction ?

Answer 1

Consider a reaction A → B

The above reaction is spontaneous in backward direction.

Then, the backward reaction is endothermic. The endothermic reaction is a reaction which involves absorption of heat from the surrounding. As given, the backward reaction is spontaneous, the highly disorderliness factor (ΔS) will be positive for backward reaction or it will be negative for forward reaction.