When the free-energy change (AG) of a reaction is negative, the reaction is said to be: Endergonic Non spontaneous Spontaneous Endothermic

Spontaneous

Explanation:

For a spontaneous reaction, the value for the change in free energy or gibbs' free energy is negative.

The change in free energy, i. e., ΔG, denotes the maximum amount of usable energy released, as going from initial state, i. e., the reactant towards the final state, i. e., the product.

And, the sign of the ΔG, determines whether the reaction is Spontaneous or non Spontaneous or at equilibrium,

i. e.,

if

ΔG < 0, the reaction is Spontaneous

ΔG > 0, the reaction is non Spontaneous

ΔG = 0, the reaction is at equilibrium

For,

ΔG < 0, that the reaction proceed without any energy input, hence, it is Spontaneous in nature.