A reaction, A + B → C + D + q is found to have a positive entropy change. The reaction will be

(i) possible at high temperature

(ii) possible only at low temperature

(iii) not possible at any temperature

(v) possible at any temperature

A reaction is said to be feasible of possible when change in Gibbs free energy for that reaction at particular temperature is negative.

We know, change in Gibbs free energy,

ΔG = ΔH – TΔS

Where

ΔH is change in enthalpy

ΔS is change in entropy

T is temperature at which reaction occurs.

Given Energy is released when a forward reaction occurs (since q is on product side), therefore ΔH is negative.

It is also given that entropy change for the reaction is positive.

Thus –TΔS would be negative for all temperatures.

Therefore,

ΔG = ΔH – TΔS would always be negative.

Thus (iv) possible at any temperature is the right answer.