(a) The Clausius inequality implies a number of criteria for spontaneous change
under a variety of conditions that may be expressed in terms of the properties of the system alone;
they are summarized by introducing the Helmholtz and Gibbs energies. (b) A spontaneous process
at constant temperature and volume is accompanied by a decrease in the Helmholtz energy.
(c) The change in the Helmholtz energy is equal to the maximum work accompanying a process
at constant temperature. (d) A spontaneous process at constant temperature and pressure is
accompanied by a decrease in the Gibbs energy. (e) The change in the Gibbs energy is equal to the
maximum non-expansion work accompanying a process at constant temperature and pressure