The determination of Gibbs energy of the exchange reaction of sulphides using beta-alumina solid electrolyte

Abstract

EMF measurements of the cell Na (l) |β″-alumina | Na₂S + A9₂S + Ag were carried out in the temperature range of 463.4 to 843.7 K. The results were represented by the equationE/V (±0.00057) = 1.75793(±0.00086) − 4.452(±0.014) × 10⁻⁴(T) where 463.4 < T < 737.7 K. The Gibbs energy of the exchange reaction 1/2Ag₂S(s) + Na(l) →1/2Na₂S(s) + Ag(s) was determined from the EMFs. The standard Gibbs energy of formation of Na₂S in the reaction 2Na(l) + 1/2S₂(g) = Na₂S(s) was obtained from the values of EMF and$\Delta G_{Ag_2 S}^0$ in the literature as$\Delta G_{Na_2 S}^0$ (J mol⁻¹ ± 1160) = −427940 + 124.92T where 463.4 < T < 737.7 K. The eutectic temperature of the Ag₂S-Na₂S system was estimated to be 738 ± 5 K.