Gibbs energy of formation of SO2. A high temperature electrochemical study

Abstract

The Gibbs energy of formation of SO2 has been measured by an e.m.f. technique with a solid electrolyte, corresponding to the cell: SO2+ S2, Au, Pt |ZrO2+ CaO| Pt, O2., (ptot≃ 1 atm)(po2≃ 1 atm) Gas mixtures with from 0.1 to 10 % S2 were used. For the reaction: S2+ 2O2= 2SO2(1) the following Gibbs energy change in the temperature range 1100–1700 K is obtained: ΔG°1=–724 300 + 150.3 TJ mol–1., This expression is from 2 to 10 kJ more positive than compiled data, and may explain discrepancies that were previously found between calculated and observed equilibria between sulphides and oxides of iron and zinc and between copper and copper sulphide, and the corresponding gas compositions.