What is the formula for Gibbs energy in thermodynamic terms?

The formula for Gibbs energy, also known as Gibbs free energy, is indeed correctly identified as G = H - TS. This expression plays a crucial role in thermodynamics as it combines aspects of enthalpy (H), temperature (T), and entropy (S) to determine the spontaneity of a process at constant temperature and pressure.

In this formula, H represents the enthalpy of the system, which accounts for the total heat content and pressure-volume work. The term TS represents the energy that cannot do work, specifically the contribution of entropy multiplied by temperature. By subtracting the TS term from H, we arrive at G, which helps predict whether a process will occur spontaneously. A negative change in Gibbs free energy (ΔG < 0) indicates that a reaction occurs spontaneously; a positive change (ΔG > 0) suggests that the reaction is non-spontaneous.

This relationship is fundamental in physical chemistry as it balances the energy available for performing work (enthalpy) against the energy lost to disorder (entropy), thus providing insight into the conditions under which chemical reactions and phase changes are favorable or not.