Under what conditions the heat evolved and absoebed in a reacrion is equal to its free energy change?

The heat evolved and absorbed in a reaction is equal to free energy change when change in entropy of a system is zero i.e., there is no change in randomness of system.
∆G = ​∆H - T​∆S
where ​∆G is free energy change, ​∆H is enthalpy change (tells abot the reaction is exothermic or endothermic) of reaction and ​∆S is entropy change.
From the relation it is clear that ​∆G will be equal to ​∆H when ​∆S is zero.