Re-evaluation of Stoichiometric Dissociation Constants from Electrochemical Cell Data for Formic Acid at Temperatures from (0 to 60) °C and for Some Other Aliphatic Carboxylic Acids at (18 or 25) °C in Aqueous Potassium Chloride Solutions

Abstract

Equations were determined for the calculation of stoichiometric (molality-scale) dissociation constants, Km, of monoprotic aliphatic carboxylic acids in buffer solutions containing formic acid, acetic acid, or some other weak acids of this kind and potassium chloride from the thermodynamic dissociation constants, Ka, of the acids and the molalities of the components in the solutions. These equations apply for formic acid to temperatures from (0 to 60) °C and were based on the single-ion activity-coefficient equations of the Huckel type. The parameters of formic acid species for these equations and the thermodynamic dissociation constants of this acid at various temperatures were determined from the Harned cell data of Harned and Embree (1934). All calculations from these data were revised, and the final parameter values obtained are independent of the temperature. The interaction parameters between hydrogen and chloride ions were taken from the results of a previous HCl paper (2002). The parameters that r...