Mass-spectrometric determination of enthalpies of dissociation of gaseous complex fluorides into neutral and charged particles. VII. MF-ThF4 systems (M = Li, Na, K, Rb, Cs)

The effusion method together with mass spectral analysis is used to study ion/molecule equilibria, involving the ThF₅⁻ ion, and equilibria between neutral species, involving NaThF₅ molecules. The experimental data obtained made it possible to calculate the enthalpies of formation of ThF₅⁻:

• 1.

  Δ H_298,f⁰, (ThF₅⁻) = −2432.4 ±12.5 kJ mol⁻¹ and NaThF₅:

• 2.

  ΔH_298,f⁰ (NaThF₅) = −2339.7 ±13.8 kJ mol⁻¹ and estimate the following enthalpies:

• 3.

  ΔH_298,f⁰ (LiThF₅) = −2373.2±18.0 kJ mol ⁻¹ li]ΔH_298,f⁰ (KThF₅) = −2381.5±15.5 kJ mol⁻¹

• 4.

  ΔH_298,f⁰ (RbThF₅) = −2393.2 ±20.9 kJ mol⁻¹

• 5.

  ΔH_298,f⁰ (CsThF₅) = −2393.7 ±17.2 kJ mol⁻¹

Activities in the system NaF-ThF₄ were determined and estimated in the systems MF-ThF₄, where M = Li, K, Rb or Cs. The equations are given for calculating the activities at temperatures from 800 to 1300 K.