Conductometric determination of dissociation constants of several acids and their tetrabutylammonium salts in propan-2-ol/water mixtures

The limiting molar conductances and dissociation constants of perchloric, hydrochloric, picric and benzoic acids as well as their tetrabutylammonium salts have been determined conductometrically in propan-2-ol/water mixtures in the whole composition range at 25 °C.The variation of Walden product (conductance times viscosity) with solvent composition shows a maximum for all the acids studied at the mole fraction of propan-2-ol of about 0.1, whereas the Walden product of the salts shows a constant value irrespective of the solvent composition. The pK of dissociation of all the studied electrolytes fits very well a general equation developed previously to relate the dissociation constants with the compositions in binary solvent mixtures. The determined parameters of this equation for each one of the studied electrolytes allow the interpolation of the pK value at any solvent composition in propan-2-ol/water mixtures.