Dissociation Energies of BeF and BeCl and the Heat of Formation of BeCIF

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 ΔHf298 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.