Collect. Czech. Chem. Commun. 2010, 75, 21-31
Published online 2009-12-06 18:37:52

Verification of accuracy of standard thermodynamic data of inorganic electrolytes

Jan Balej

Heřmanova 35, 170 00 Prague 7, Czech Republic


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 ΔGşf,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.