The enthalpies of formation of XeF6(c), XeF4(c), XeF2(c), and PF3(g)

The energies of reaction of XeF₆(c), XeF₄(c), and XeF₂(c) with PF₃(g) were measured in a bomb calorimeter. These results were combined with the enthalpy of fluorination of PF₃(g), which was redetermined to be −(151.98 ± 0.07) kcal_th mol⁻¹, to derive (at 298.15 K) ΔH_f^o(XeF₆, c, I) = −(80.82 ± 0.53) kcal_th mol⁻¹, ΔH_f^o(XeF₄, c) = −(63.84 ± 0.21) kcal_th mol⁻¹, and ΔH_f^o(XeF₂, c) = −(38.90 ± 0.21) kcal_th mol⁻¹. The enthalpies of formation of the solid xenon fluorides were combined with reported enthalpies of sublimation to derive (at 298.15 K) ΔH_f^o(XeF₆, g) = −(66.69 ± 0.61) kcal_th mol⁻¹, ΔH_f^o(XeF₄, g) = −(49.28 ± 0.22) kcal_th mol⁻¹, and ΔH_f^o(XeF₂, g) = −(25.58 ± 0.21) kcal_th mol⁻¹. The average bond dissociation enthalpies,〈D^o〉(XeF, 298.15 K), are (29.94 ± 0.16), (31.15 ± 0.13), and (31.62 ± 0.16) kcal_th mol⁻¹ in XeF₆(g), XeF₄(g), and XeF₂(g), respectively. The enthalpy of formation of PF₃(g) was determined to be −(228.8 ± 0.3) kcal_th mol⁻¹.