Vaporization of LnCl 3 and thermochemistry of Ln 2Cl 6(g), Ln=Ce, Pr, Nd, Dy

Abstract

The vaporization of LnCl 3, Ln=Ce, Pr, Nd, Dy, was investigated by Knudsen effusion mass spectrometry. The monomer and dimer partial pressures in the equilibrium vapor of the compounds were determined. Molecular parameters of LnCl 3(g) and Ln 2Cl 6(g) were determined theoretically and the thermodynamic functions of these species were computed applying statistical thermodynamics. The enthalpies of sublimation of LnCl 3(g) were evaluated according to the second- and third-law methods. Recommended values of Δ sub H o(298)=334.8±7.2 kJ mol −1 (CeCl 3), 323.3±3.5 kJ mol −1 (PrCl 3), 317.3±6.4 kJ mol −1 (NdCl 3), and 305.3±6.3 kJ mol −1 (DyCl 3), resulted for the sublimation enthalpies of gaseous species given in brackets by compilation of the present study with the data available in the literature. The enthalpies of sublimation Δ sub H o(298)=443.2±12.0 kJ mol −1 (Ce 2Cl 6), 418.7±12.1 kJ mol −1 (Pr 2Cl 6), 414.8±11.3 kJ mol −1 (Nd 2Cl 6), and 354.1±11.3 kJ mol −1 (Dy 2Cl 6), were obtained for dimeric species by the use of the third law method.