Thermodynamic Study of Tin Sulfide and Lead Sulfide Using a Mass Spectrometer

Abstract

A mass‐spectrometric investigation of the vapor in equilibrium with solid SnS, solid PbS, and a mixture of SnS and PbS has yielded the following reaction enthalpies: $$\begin{array}{cc}\mathrm{SnS}(\mathrm{s}\mathrm{)\to }\mathrm{SnS}(\mathrm{g})& {\mathrm{\Delta H}}_{298}^0\text{=52.6±1.6\hspace{0.17em}}\mathrm{kcal}/\mathrm{mole}\\ 2\mathrm{SnS}(\mathrm{s}\mathrm{)\to }{\mathrm{Sn}}_2{\mathrm{S}}_2(\mathrm{g})& \text{56.5±5.0}\\ \mathrm{PbS}(\mathrm{s}\mathrm{)\to }\mathrm{PbS}(\mathrm{g})& \text{55.7±1.6}\\ 2\mathrm{PbS}(\mathrm{s}\mathrm{)\to }{\mathrm{Pb}}_2{\mathrm{S}}_2(\mathrm{g})& \text{66.6±5.0}\\ \mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}\mathrm{PbS}(\mathrm{g}\mathrm{)\to }\mathrm{Pb}(\mathrm{g}\mathrm{)+}\frac{1}{2}{\mathrm{S}}_2(\mathrm{g})& \text{28.8±2.6}\\ {\mathrm{Sn}}_2{\mathrm{S}}_2(\mathrm{g}\text{)→2}\mathrm{SnS}(\mathrm{g})& \text{48.7±5.0}\\ {\mathrm{Pb}}_2{\mathrm{S}}_2(\mathrm{g}\text{)→2}\mathrm{PbS}(\mathrm{g})& \text{44.8±5.0}\\ \mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}{\mathrm{SnPbS}}_2(\mathrm{g}\mathrm{)\to }\mathrm{SnS}(\mathrm{g}\mathrm{)+}\mathrm{PbS}(\mathrm{g})& \text{46.5±5.0.}\end{array}$$ The dissociation energies of gaseous SnS and PbS were determined to be D₀⁰(SnS) = 110.1±3.0 kcal/mole, D₀⁰(PbS) = 79.1±2.8 kcal/mole and are compared with the spectroscopically determined values.