DEGREES OF FREEDOM IN A GASEOUS REACTION SYSTEM AT A SPECIFIED PARTIAL-PRESSURE OF A REACTANT

In the usual equilibrium calculation on a reaction system at specified temperature and pressure, the criterion of chemical equilibrium can be expressed in terms of the Gibbs energy G, and the system is represented by a conservation matrix A or a stoichiometric number matrix nu, which are equivalent. However, in an equilibrium calculation at specified temperature, pressure, and partial pressures of one or more species, the criterion of chemical equilibrium must be expressed in terms of the transformed Gibbs energy G, and the system is represented by an apparent conservation matrix A' or an apparent stoichiometric number matrix nu', which are equivalent. This reconceptualization of the equilibrium calculation leads to the use of the number N' of pseudospecies, the number R' of apparent independent reactions, the number C' of apparent components, and the number F' of apparent degrees of freedom. These numbers are all less than the usual N, R, C, and F. Matrix multiplication is used to translate the A matrix from one set of components to another. Several specific cases are discussed.