Question

Why is Gibbs free energy useful?

Answer 1

Why....?

Explanation:

Well, to quote a text-book, the `"Gibbs free energy"` is the single, unequivocal criterion as to the spontaneity of chemical change...

And it is normally introduced by quoting an enthalpy term, and an entropy term...i.e...

`DeltaG^@=DeltaH^@-TDeltaS^@`...

...and this function can be further related to the thermodynamic equilibrium constant for a given reaction....by the relation....

`lnK_"eq"=(-DeltaG^@)/(RT)`

And quite clearly, ONLY negative `DeltaG^@` values will give rise to a positive `K_"eq"` value, and thus only reactions with negative `DeltaG^@` values are spontaneous.