Abstract
The following definitions and examples are based on recent recommendations by the Union of Pure and Applied Chemistry (Ewing et aZ., 1994; cf. also the recommendations given in Mills et ai., 1993). Further details can be found in textbooks on chemical thermodynamics (e.g. McGlashan, 1979).
According to IUPAC, all standard chemical potentials and standard equilibrium constants are defined in terms of an arbitrarily chosen standard pressure. Alternative definitions with explicit pressure dependencies of these quantities are possible for reactions in condensed phases (e.g. Wood and Battino, 1990). This, however, requires different relationships for reactions in condensed and gaseous phases, because for the latter the standard thermodynamic quantities are usually defined for a standard pressure of 1 bar.