Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Accuracy of standard thermodynamic data for some inorganic electrolytes of the types 1-1, 1-2 and 2-1 at 25 °C, in the solid state or aqueous standard solutions, presented in NBS Tables (1982), has been checked. For the purpose, the condition for the pure solid–saturated solution equilibrium and reliable values of solubilities, mean activity coefficients and water activity in saturated solution at the given temperature were used. In most cases, a very good reliability and consistency of all relevant data have been found. On the other hand, some discrepancies have been observed for NaNO₃, NaClO₄/NaClO₄ pair, Na₂HPO₄·12H₂O/Na₂HPO₄ pair, K₂CrO₄, K₂Cr₂O₇, (NH₄)₂SO₄ and SrCl₂·6H₂O/SrCl₂ pair the reason of which is not yet known. The verification method can be used for the determination of lacking thermodynamic data. The method has been applied to ΔGş_f,cr of NaCNS·2H₂O, NaH₂PO₄·2H₂O, Na₂CrO₄·6H₂O, Na₂WO₄·2H₂O, MgI₂·8H₂O and CaCl₂·6H₂O at 25 °C. A suitable method has been used for the determination of the most probable solubility in the case when the values scatter. The used methods are applicable to all types of electrolytes and nonelectrolytes.

Keywords: Standard thermodynamic data; Inorganic electrolytes; Accuracy; Verification.

References: 14 live references.