Thermodynamics of mixed and pure aqueous solutions of K2HPO4 at T=298.15 K

Abstract

Experimental results on isopiestic measurements for three ternary aqueous solutions of K2HPO4 with KCl, KBr, and KNO3 at T = 298.15 K were modeled with the Clegg-Pitzer-Brimblecombe equation based on mole-fraction-composition scale yielding appropriate mixing parameters, for the estimation of thermodynamic activities of solute components. The results for mean ionic activity coefficients of electrolytes in ternary solutions, calculated this way, are showing specific behavior depending on total ionic strength and ionic strength fractions of electrolytes. The activity coefficients of KCl in {yKCl + (1-y)K2HPO4}(aq) and of KBr in {yKBr + (1-y)K2HPO4}(aq) are changing consistently from the ionic strength and their ionic strength fractions contrary to activity coefficients of KNO3 in {yKNO(3) + (1-y)K2HPO4}(aq). In addition, molality of K2HPO4 aqueous saturated solution, in equilibrium with K2HPO4 center dot 3H(2)O(cr), and appropriate osmotic coefficient at T = 298.15 K, were determined by the isopiestic method.