The Gibbs free energy, also known as the Gibbs energy or G, is a thermodynamic property that describes the potential of a system to do work. It is defined as the difference between the enthalpy (H) and the product of the absolute temperature (T) and the entropy (S) of a system: G = H - TS.
The Gibbs free energy is an important concept in thermodynamics as it helps predict the spontaneity of a process and the maximum amount of work that can be obtained from a system. A negative value for G indicates that a process is spontaneous, while a positive value indicates a non-spontaneous process.
In chemical reactions, the Gibbs free energy change (ΔG) can be used to determine the direction and spontaneity of the reaction. If ΔG is negative, the reaction is spontaneous and can occur without an external energy input. If ΔG is positive, the reaction is non-spontaneous and will only occur with an external energy input.
The Gibbs free energy is also used to calculate the equilibrium constant (K) for a reaction. At equilibrium, ΔG = 0, and the reaction quotient (Q) is equal to K. If Q < K, the reaction proceeds in the forward direction, and if Q > K, the reaction proceeds in the reverse direction.
The Gibbs free energy is closely related to entropy, which is a measure of the disorder or randomness in a system. A decrease in entropy (ΔS) results in an increase in G, making a process less spontaneous. On the other hand, an increase in entropy results in a decrease in G, making a process more spontaneous.