Mass spectrometric determination of the heats of formation of the silicon subchlorides SiCl(g), SiCl2(g) and SiCl3(g)

Abstract

An effusion-mass spectrometric determination of the reaction of SiCl₄(g) with Si(c, l) in the temperature range 1593–1792 K has been completed. Second and third law reaction enthalpies were obtained for SiCl₄(g)+ Si(g)= 2SiCl₂(g), SiCl₄(g)+ SiCl₂(g)= 2SiCl₃(g), and SiCl₂(g)+ Si(g)= 2SiCl(g). From the heats of reaction third law ΔH_f298 values of 47.1 ± 0.6, –40.6 ± 0.6 and –93.3 ± 0.5 kcal mol^–1 were obtained for SiCl(g), SiCl₂(g) and SiCl₃(g), respectively. For the dissociation of SiCl(g)→(³P₀)Si(g)+(²P_3/2)Cl(g) a third law dissociation energy value of 88.6 ± 0.6 kcal mol^–1 was calculated.