Calculation of proton activity in aqueous protolyte solutions

Abstract A general and thermodynamically exact equation for the calculation of the proton (hydroxide ion) activity of aqueous solutions of monoprotic acidic (and basic) species is given. Under certain conditions, various approximate equations can be derived from the exact form; the applicability of these depends mainly on both the thermodynamic equilibrium constant, K p , of the protolytic reaction, and the stoichiometric concentration, C o , of the protolyte. Taking into account the mean ionic activity coefficients which are calculated by means of the Davies equation, diagrams are constructed exhibiting those combinations of K p and C o for which the respective approximations can be applie…