Dissociation energies of the molecules CrPO2(g) and CrO(g) by high-temperature mass spectrometry

Abstract

The gaseous molecule CrPO₂ has been investigated in the course of a high-temperature mass-spectrometric Knudsen-cell study of the vapours over an europium–chromium–phosphorus–oxygen system. From the enthalpy of the equilibrium reaction CrPO₂(g)= CrO(g)+PO(g) and appropriate ancillary data, the atomization energy of this molecule has been determined. In addition, the dissociation energy of CrO(g) has been obtained through the study of the gaseous exchange reactions WO₃(g)+ Cr(g)= WO₂(g)+CrO(g) and EuO(g)+Cr(g)= Eu(g)+CrO(g), and compared with previous results.

The dissociation energies obtained are: ΔH^⊖_0,at(CrPO₂)= 1438.4±12.2 kJ mol^–1, and D^⊖₀(CrO)= 436.2±8.9 kJ mol^–1.

The appearance potential of CrPO₂(g) was determined to be 8.0±0.5 eV, and the heat of formation was derived as: ΔH^⊖_0,f[CrPO₂(g)]= 217.6±13.0 kJ mol^–1.