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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, Δ H298°(kcal), for the following reactions: Sb4(g)=2Sb2(g) (71.3 ± 1.8), Sb4(g) =4Sb(g) (215.0 ± 3.0), Sb2(g) = 2Sb(g) (71.8 ± 1.0), Sb3(g)=3Sb(g)(129 ± 4), P2(g) =2P(g) (117.1 ± 1.1), Sb2(g) + P2(g) = 2SbP(g) (17.6 ± 0.4), SbP(g) = Sb(g)+P(g) (86.0 ± 1.2), and 2SbP3(g)=Sb2(g)+3P2(g) (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 Δ H°f,298 of the molecules given. D298°kcal mol−1or kJ mol−1Δ Hf,298°kcal mol−1or kJ mol−1Sb271.8 ± 1.0300.4 ± 4.854.7 ± 2.2288.7 ± 9.2Sb3129.0 ± 4.0539.7 ± 16.760.7 ± 5.8254.0 ± 24.3Sb4215.0 ± 3.0899.6 ± 12.637.9 ± 5.4158.6 ± 22.6SbP85.7 ± 0.9358.6 ± 3.857.3 ± 1.6239.8 ± 6.7SbP3285.8 ± 5.21195.8 ± 21.816.8 ± 6.070.3 ± 25.1
Kordis et al. (Fri,) studied this question.