Study of the electronic structure of molecules. VII. Inner and outer complex in the NH₄Cl formation from NH₃ and HCl

Abstract

Analysis of the variation of the internuclear distances and of the frequencies in the formation of NH4Cl from NH3 and HCl indicates that for the NH4Cl molecule there are two rather distinct regions for the molecular complex, both stable with respect to the component molecules NH3 and HCl. Contrary to previous assumptions, no outer complex was found. The potential surface of the two regions goes into one another smoothly since there is no activation barrier between the two complexes. From computations, estimates of the frequencies, and from the computed value of the dissociation energy of NH4Cl with respect to NH3 and HCl, it is found that at temperatures around 400°C and at one atomosphere of pressure the NH4Cl molecule dissociates almost totally into NH3 and HCl. This is in agreement with experimental data. It is, therefore, proved that the assumption of an outer complex and of an activation barrier is unnecessary for the explanation of the NH4Cl dissociation process into NH3 and HCl. Tables of the equilibrium constant at various temperatures and of other thermodynamic data are presented.