EMCC Biology Test 2 Practice 2026 - Free Biology Practice Questions and Study Guide

A negative free energy change (ΔG) indicates that a reaction is spontaneous under the given conditions. In thermodynamics, a spontaneous reaction is one that can occur without the need for additional energy input from an external source. This is because the system is moving toward a more stable state, and the energy that is released can be harnessed to do work.

When ΔG is negative, it signifies that the reactants have higher free energy compared to the products, meaning that the transition from reactants to products is energetically favorable. Thus, the reaction can proceed on its own. The magnitude of ΔG can also provide insight into how far the reaction is from equilibrium and how much energy is available to do work.

In contrast, a positive ΔG would indicate that energy is required for the reaction to proceed, suggesting that it is non-spontaneous. Equilibrium implies that the rates of the forward and reverse reactions are equal, which corresponds to a ΔG of zero. An endergonic reaction is characterized by a positive ΔG, indicating that it absorbs energy. Therefore, a ΔG of -31.45 kJoules clearly indicates that the reaction is spontaneous.