Measurement of the standard molar Gibbs free energy of formation of Ag 2S using Ag +β-alumina solid electrolyte

Abstract

Ag +β-alumina has been employed as a solid electrolyte in order to measure the activities of silver for Ag 2S in equilibrium with controlled sulphur atmospheres. Electromotive-force measurements were made in the temperature range 811 K to 1112 K using the galvanic cell: Pt|Ag|Ag +β-Al 2O 3|Ag 2S, MoS 2| (1 − x 2− x 3)N 2+ x 2H 2+ x 3H 2S|Pt. Manipulation of the results yielded for the standard molar Gibbs free energy of formation of Ag 2S with respect to pure Ag(s) and S 2(g) at p o= 101.325 kPa: 2Ag(s) + 1 2 S 2(g) = Ag 2S(s), Δ fG o m/(J·mol -1) = {− 85326 + 35.15( T/K)} ± 2500.