1. The problem statement, all variables and given/known data It is given in my book that: ΔStotal=ΔSsystem+ΔSsurrounding Where S is entropy. ΔSsurr=-ΔH/T Therefore: ΔStotal=ΔSsystem+[-ΔHsystem/T] As we can see here that ΔSsurrounding=-ΔHsystem/T is applied here . But is this relation correct? 2. Relevant equations ΔS=qreversible/T Where qreversible is the heat input which is equal to ΔH(enthalpy) for constant P and T. 3. The attempt at a solution What I think is that , instead of ΔHsystem there should be ΔHsurroundings Since the change in entropy of surroundings is taken. Am I correct here?