Topic overview

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Gibbs energy is defined as G = H − TS and is a state function. At constant temperature and pressure, a negative ΔG indicates a spontaneous process, while ΔG = 0 marks equilibrium; the Second Law can therefore be expressed as evolution toward minimum G. The lesson develops the differential form dG = −S dT + V dP and explains chemical potential as the partial molar Gibbs energy that helps govern phase and chemical equilibria. It also links activities to chemical potential in ideal mixtures and standard Gibbs changes to equilibrium constants. Further applications include temperature effects, phase transitions, maximum non-PV work, and the relation between Gibbs energy change and electrochemical cell voltage.