IUPAC - A REPORT OF IUPAC COMMISSION 1.2 ON THERMODYNAMICS - STANDARDQUANTITIES IN CHEMICAL THERMODYNAMICS - FUGACITIES, ACTIVITIES, AND EQUILIBRIUM-CONSTANTS FOR PURE AND MIXED PHASES

The standard chemical potential mu degrees is defined in terms of a sp ecified state of aggregation, a specified temperature, a specified sta ndard pressure, and if needed a specified standard molality. Other sta ndard thermodynamic quantities are obtained from mu degrees by the usu al mathematical operations. In this report, definitions are given for the standard chemical potential of a substance B in the following stat es of aggregation: gas phase whether pure or mixed, condensed phase wh ether pure or mixed, solvent substance in solution, and solute substan ce in solution. Fugacities and virial coefficients are introduced in t he discussion of gases, and activity, activity coefficients, and osmot ic coefficients in the discussion of condensed phases. Expressions for the standard equilibrium constant are given for a reaction in the gas phase, in a condensed phase, and in a solution. Some numerical exampl es are given and relative magnitudes of various terms in the equations are illustrated.