Thermodynamic Models for Correlation of Solubility of Hexaquocobalt(II) Bis(p-toluenesulfonate) in Liquid Mixtures of Water and Ethanol from 288.15 to 333.15 K

Abstract

The solubilities of hexaquocobalt(II) bis(p-toluenesulfonate) [Co(OTs)2·6H2O] in water and ethanol mixed solvents with ethanol mole fractions of 0–0.342 were determined from 288.15 to 333.15 K by a synthetic method. The generated data were well correlated with the modified Apelblat equation, the Redlich–Kister (CNIBS/R–K) model, and the hybrid model in which the mean deviations are less than 3.06 %. Materials Studio DMol3 (Accelrys Software Inc.) was chosen to investigate the molecular modeling. The results indicated that the increase of solubility of Co(OTs)2·6H2O with increase of the initial mole fraction of ethanol (x2) is due to stronger interactions occurring between ethanol and Co(OTs)2·6H2O. Moreover, this tends to level out when x2 is greater than 0.228 because some new clusters will be formed by the water and ethanol molecules in the binary mixture. The modified van’t Hoff equation was adopted to analyze the enthalpy, entropy, and Gibbs energy, indicating the dissolution process of Co(OTs)2·6H2O in mixed solvents is endothermic, spontaneous, and entropy driven.