Which equation correctly expresses Gibbs free energy in terms of enthalpy and entropy?

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Gibbs free energy combines the heat content of a system with the effect of disorder to predict spontaneity at constant temperature and pressure. The correct relation is G equals H minus TS, where H is enthalpy (the energy content at constant pressure) and TS represents the portion of energy tied up in increasing disorder that cannot be used to do work. This comes from starting with G = U + PV − TS and recognizing that enthalpy H is U + PV, so G = H − TS. At constant temperature and pressure, the change in Gibbs energy is ΔG = ΔH − TΔS, so processes with negative ΔG can proceed spontaneously because they release usable energy even while entropy is increasing. The TS term thus lowers G when entropy increases, capturing how disorder competes with enthalpy to determine feasibility. While rearranging G = H − TS gives H = G + TS, the form G = H − TS is the standard way we express the relationship directly.