Mass spectroscopic investigation of the equilibrium dissociation of gaseous Sb2, Sb3, Sb4, SbP, SbP3, and P2

Knudsen effusion mass spectroscopic studies of the vapor above a gadolinium antimonide‐molybdenum phosphide‐graphite system led to the determination of the standard enthalpy changes, ${\mathrm{\Delta \; H}}_{298}\mathrm{°(}\mathrm{kcal})$ , for the following reactions: ${\mathrm{Sb}}_4(\mathrm{g}\text{)=2}{\mathrm{Sb}}_2(\mathrm{g}\text{) (71.3 ± 1.8)}$ , ${\mathrm{Sb}}_4(\mathrm{g}\text{) =4}\mathrm{Sb(g)}\text{(215.0 ± 3.0)}$ , ${\mathrm{Sb}}_2(\mathrm{g}\text{) = 2}\mathrm{Sb}(\mathrm{g}\text{) (71.8 ± 1.0)}$ , ${\mathrm{Sb}}_3(\mathrm{g}\text{)=3}\mathrm{Sb(g)}\text{(129 ± 4)}$ , ${\mathrm{P}}_2(\mathrm{g}\text{) =2}\mathrm{P(g)}\text{(117.1 ± 1.1)}$ , ${\mathrm{Sb}}_2(\mathrm{g}\mathrm{)\; +}{\mathrm{P}}_2(\mathrm{g}\text{) = 2}\mathrm{SbP(g)}\text{(17.6 ± 0.4)}$ , $\mathrm{SbP(g)}=\mathrm{Sb(g)}+\mathrm{P(g)}\text{(86.0 ± 1.2)}$ , and $2{\mathrm{SbP}}_3(\mathrm{g}\mathrm{)=}{\mathrm{Sb}}_2(\mathrm{g}\text{)+3}{\mathrm{P}}_2(\mathrm{g}\text{) (149 ± 8)}$ . These reaction enthalpies have been combined with appropriate literature data to obtain the dissociation or atomization energies D°₂₉₈ and standard heats of formation ${\mathrm{\Delta \; H°}}_{\text{f,298}}$ of the molecules given. $$\begin{array}{ccccc}& \frac{D_{298}°}{{\mathrm{kcal\; mol}}^{\text{−1}}{\mathrm{or\; kJ\; mol}}^{\text{−1}}}& & \frac{{\mathrm{\Delta \; H}}_{\text{f,298}}°}{{\mathrm{kcal\; mol}}^{\text{−1}}{\mathrm{or\; kJ\; mol}}^{\text{−1}}}& \\ {\mathrm{Sb}}_2& \text{71.8 ± 1.0}& \text{300.4 ± 4.8}& \text{54.7 ± 2.2}& \text{288.7 ± 9.2}\\ {\mathrm{Sb}}_3& \text{129.0 ± 4.0}& \text{539.7 ± 16.7}& \text{60.7 ± 5.8}& \text{254.0 ± 24.3}\\ {\mathrm{Sb}}_4& \text{215.0 ± 3.0}& \text{899.6 ± 12.6}& \text{37.9 ± 5.4}& \text{158.6 ± 22.6}\\ \mathrm{SbP}& \text{85.7 ± 0.9}& \text{358.6 ± 3.8}& \text{57.3 ± 1.6}& \text{239.8 ± 6.7}\\ {\mathrm{SbP}}_3& \text{285.8 ± 5.2}& \text{1195.8 ± 21.8}& \text{16.8 ± 6.0}& \text{70.3 ± 25.1}\end{array}$$