Concentrating on the system

This chapter highlights the Helmholtz and Gibbs energies to develop the Clausius inequality. The Clausius inequality implies a number of criteria for spontaneous change under a variety of conditions which may be expressed in terms of the properties of the system alone. A spontaneous process at constant temperature and volume is accompanied by a decrease in the Helmholtz energy. The change in the Helmholtz energy is equal to the maximum work obtainable from a system at constant temperature. Meanwhile, a spontaneous process at constant temperature and pressure is accompanied by a decrease in the Gibbs energy. The change in the Gibbs energy is equal to the maximum non-expansion work obtainable from a system at constant temperature and pressure. The chapter then looks at the standard Gibbs energies of formation and the Born equation.