Free enegry , `G = H - TS`, is state function that indicates whther a reaction is spontaneous or non-spontaneous. If you think of `TS` as the part of the system's enegry that is disordered already, then `(H -TS)` is the part of the system's energy that is still ordered and therefore free to cause spontaneous change by becoming disordered.
Also, `DeltaG = DeltaH - T DeltaS` From the second law of thermodynamics, a reaction is spontaneous if `Delta_("total")S` is positive, non-spontaneous if `Delta_("total")S` is negative, and at equilibrium if `Delta_('total")S` is zero.
Since, `-T DeltaS = DeltaG` and since `DeltaG` and `DeltaS` have opposite sings, we can restate the thermodynamic criterion for the spontaneity of a reaction carried out a constant temperature and pressure.
IF `DeltaG lt 0`, the reaction is spontaneous.
If `DeltaG gt 0`, the reaction is non-spontaneous.
If `DeltaG = 0`, the reaction is at equilibrium.
Read the above paragraph carefully and answer the following questions based on the above comprehension.
A particular reaction has a negative value for the free energy change. Then at ordinary temperature

Options

A. It has a large `(-ve)` value for the entropy change
B. It has large `(+ve)` value for enthalpy change
C. It has a small `(+ve)` value for enthalpy change
D. It has a `(+ve)` value for the entropy change and a `(-ve)` value for enthalpy change.

Explanation

`DeltaG = DeltaH - T DeltaS` can be negative at ordinary temperature `T` if `DeltaH is-ve` and `DeltaS is +ve`