Thermodynamic aspects
Determination of the Constants of Acidity in Aqueous Environment

For simplicity's sake, we'll just consider binary solute-solvent solutions, with the solvent being the largest component of the mixture. The fact that only binary mixtures are studied in no way detracts from the generality of the following considerations. The solvent is designated by the subscript A, the solute by the subscript B. The three most commonly used units of "concentration" in solution chemistry are mole fraction, molality and molarity. Let n _A be the number of moles of the solvent and n _B that of the solute, and the mole fractions of each are :

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