Standard potentials of the silver–silver chloride electrode in t-butyl alcohol–water mixtures and the thermodynamics of solutions of hydrochloric acid at different temperatures

Abstract

Electromotive force measurements of cells of the type Pt,H₂(g, 1 atm)|HCl(m), Bu^tOH (X),H₂O(100 –X)|AgCl-Ag at 5, 15, 25, 35, and 45°C have been used to evaluate (i) the standard potentials of the Ag–AgCl electrode for X= 10, 20, 40, and 70%(w/w) by a polynomial curve-fitting technique, (ii) the mean molal activity coefficients of hydrochloric acid (0·005–0·2 mol kg^–1), (iii) the primary medium effects, (iv) the relative partial molal enthalpies, and (v) the thermodynamic functions for the transfer of HCl from water to the respective solvent media. The values of E_m° in each solvent have been represented as a function of temperature. The significance of the results has been discussed in relation to the acid–base properties and the breakdown of the structure of water on the addition of t-butyl alcohol.