Fundamental Equations and Their Relationships
This chapter examines the properties and interrelationships of the thermodynamic potentials (state functions) H (the enthalpy), A (the Helmholtz free energy), G (the Gibbs free energy), and µi (the chemical potential of the species i). The Helmholtz free energy thus provides a criterion for equilibrium in a system at constant temperature and constant volume. The Gibbs free energy of a simple closed system with no chemical reactions depends only on the temperature and the pressure. The number of moles of the various species present can change as the consequence of a chemical reaction occurring in the system. If the system is an open system, since the Gibbs free energy is an extensive property, its value is dependent on the amount of matter of the system. The chapter looks at the fundamental equation which uses G' as the dependent variable and temperature, pressure, and magnetic field as the independent intensive variables.