How does ΔG relate to the spontaneity of a reaction?

The concept of Gibbs free energy (ΔG) is crucial in understanding thermodynamics as it relates to chemical reactions. In this context, a negative ΔG indicates that the reaction can occur spontaneously, meaning it can proceed in the forward direction without the input of external energy. This relationship is rooted in the second law of thermodynamics, which suggests that spontaneous processes tend to move toward a state of lower energy and greater entropy.

When ΔG is negative, it implies that the products of the reaction are lower in free energy than the reactants, driving the reaction toward completion. Conversely, a positive ΔG would indicate that a reaction is non-spontaneous under standard conditions, meaning that energy would need to be supplied for the reaction to proceed.

Thus, the correct understanding aligns with the assertion that a negative ΔG signifies spontaneity. This principle is fundamental in biochemistry, as many biochemical reactions are regulated by changes in Gibbs free energy, impacting metabolic pathways and energy production within biological systems.