Dissociation energies of BeF and BeCl and the heat of formation of BeClF

Abstract

An effusion-mass spectrometric investigation of the Be–Cl–F system to obtain bond energies of BeF and BeCl and the heat of formation of the mixed halide BeClF has been completed. A study of the ion intensities of the species produced in the simultaneous reaction of chlorine gas and BeF₂ vapour with elemental beryllium was made in the temperature range 1415 to 1592 K. The reaction enthalpies calculated from these species yield second and third law ΔH_f298 values of –139.0 ± 4 and –140.5 ± 2 kcal mol^–1, respectively, for BeClF(g). The dissociation energies of 104 kcal mol^–1 obtained for BeCl and 144 kcal mol^–1 for BeF agree with those previously reported from spectroscopic, molecular flow effusion, and transport investigations.