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), ButOH (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 Em° 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.