Thermodynamic Study of the Gaseous Heterocomplexes NaSnCl₃ and NaSnBr₃

The NaCl – SnCl 2 and NaBr – SnBr 2 systems were investigated under equilibrium conditions in the temperature ranges between 713 to 963 K and 653 to 893 K, respectively, by using Knudsen effusion mass spectrometry with a two‐compartment Knudsen cell. The gaseous species NaX, (NaX) 2 , SnX 2 , and NaSnX 3 (X = Cl, Br) are present in the vapour of the two systems. The enthalpy and entropy changes of the dissociation reactions NaSnCl 3 (g) ⇄ NaCl(g) + SnCl 2 (g) (1) and NaSnBr 3 (g) ⇄ NaBr(g) + SnBr 2 (g) (2) resulted as Δ H o 298 (Eq. (1)) = 197 ± 6 kJ mol −1 , Δ S o 298 (Eq. (1)) = 153 ± 7 J mol −1 K −1 , Δ H o 298 ,(Eq. (2)) = 190 ± 6 kJ mol −1 , and Δ H o 298 (Eq. (2)) = 160 ± 7 J mol −1 K −1 . The enthalpy and entropy changes of the reactions SnX 2 (g) + (NaX) 2 (g) ⇄ NaSnX 3 (g) NaX(g), X = Cl, Br, (3) are additionally evaluated as well as equilibrium constants for the reactions Eqs. (1) to (3). The results obtained are discussed.