Anion-specific effects on activity coefficients in aqueous solutions of sodium salts: Modeling with the extended Debye–Hückel theoryстатья
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Аннотация:The extended Debye–Hückel theory, which allows for concentration variation of electro-
lyte solution static permittivity, is employed to predict activity coefficients in aqueous solu-
tions of sodium salts with various univalent anions (NaCl, NaBr, NaI, NaNO 3 , NaClO 4 and
NaSCN) at ambient conditions. Calculations without empirical adjustments reproduced the
activity coefficients for NaI in the concentration range up to 6 mol·kg −1 and for NaSCN
up to 2 mol·kg −1 . In the case of other solutions, calculations underestimate water activ-
ity coefficients and overestimate mean ionic activity coefficients at concentrations beyond
0.5 mol·kg −1 . In order to improve the representations, the model was extended to include
ion pairing, which resulted in a better agreement between calculated activity coefficients
and experimental data, especially for NaNO 3 . The ion pairing equilibrium constants were
estimated and compared with available literature values. The extent of ion pairing was
found to increase in the sequence NaI < NaSCN < NaBr < NaCl < NaClO 4 < NaNO 3 ,
with violation of the Collins rule in the case of polyatomic oxygen-containing anions.