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Composition and thermochemistry of the equilibrium vapour of the systems NaI—FeI 2 and NaI—PbI 2

1987; Volume: 91; Issue: 3 Linguagem: Inglês

10.1002/bbpc.19870910308

0005-9021

K. Hilpert, H. Gerads, Dietmar Kobertz, M. Miller,

Luminescence Properties of Advanced Materials

Abstract The vaporization of NaI/FeI 2 and NaI/PbI 2 samples of equimolar composition was investigated in the temperature ranges between 574 to 683 K and 562 to 669 K, respectively, by using the mass spectrometric Knudsen effusion method. The gaseous species I. I 2 , Nal. (NaI) 2 FeI 2 , (FeI 2 ) 2 , FeI 3 , NaFel 3 , and Na 2 FeI 4 (NaI—FeI 2 system) as well as Nal, (Nal) 2 , PbI 2 , (PbI 2 ) 2 , and NaPbI 3 (NaI—PbI 2 system) are present in the equilibrium vapours. The equilibrium partial pressures of these species were determined with the exception of I, I 2 , and Fel 3 . Enthalpies and entropies of dissociation resulted for the reactions magnified image as Δ d H 298 0 (Eq. (1)) = 184 ± 5 kJ mol −1 , Δ d H 298 0 (Eq. (1)) = 043 ± 8 j mol −1 K −1 ;Δ d H 298 0 (Eq. (2)) = 333 ± 9 kj mol −1 , Δ d H 298 0 (Eq. (2)) = 274 ± 14 J mol −1 K −1 ; and Δ d H 298 0 (Eq. (3)) = 168 ± 5 J mol −1 , Δ d H 298 0 (Eq. (3)) = 151 ± 9 j mol −1 K −1 . Equilibrium constants for these reactions are additionally given. The pressures of NaFel 3 (g) and NaPb1 3 (g) as well as their enthalpies of dissociation are discussed with respect to their significance for semi empirical rules.