PbSe g

Uy and Drowart [69UY/DRO] found PbSe(g) to be the major species in gaseous mixtures of lead and selenium using mass spectrometry. The vaporisation of PbSe(cr) occurs according to the reaction PbSe(cr) PbSe(g). 

Second law entropies were calculated by the review as discussed in Appendix A from the evaporation studies summarised in Table V-40. The second laws values agree well with the value calculated from molecular data. 

15 K) = (228.0 + 4.2) kJ mol. The selected value of the enthalpy of formation of PbSe(g) is calculated from the selected value of the sublimation enthalpy and the enthalpy of formation of PbSe(cr) yielding  

The Gibbs energy of formation is calculated from the selected enthalpy of formation and entropy of PbSe(g), the selected entropy of selenium, and the entropy of lead in [89COX/WAG] to be  

---

Table V-40 Second law entropy values for PbSe(g) at 298.15 K derived from vapour pressure measurements as discussed in Appendix A.

The evaporation of PbSe(cr) was studied in the temperature range 835 to 1047 K using the torsion effusion technique. The original evaluation employed auxiliary data different from those used by the review and the vapour pressure expression was therefore reevaluated using the selected values of the entropies and heat capacities of PbSe(cr) and PbSe(g). The second law entropy of PbSe(g) and the second law enthalpy of sublimation of PbSe(cr) were calculated to be S°(PbSe, g, 298.15 K) = (260.6 + 7.0)... 

PbSe[g] LEAD SELENIDE (GAS) 1308 PuH3 PLUTONIUM TRIHYDRIDE 1349... 

---