The investigation of ionic association in the CdF2 solution with the mixed solvent (water +ethanol +propanol) at 25°C

Abstract

Using the mixed solvents, (water +ethanol + propanol), the solubility of CdF2 was determined by<br />evaporating method at 25° C. The results showed that the sollbility, s, of CdF2 decreases by<br />decreasing the dielectric constant of the mixed solvent .Once the solubility of CdF2 was determined,<br />the concentration solubility product, Ksp(c)=4s3, was calculated .Furthermore ,by estimating the mean<br />activity coefficient, f± , of CdF2 in the solution upon the extended Debye-Hückel theory, the model<br />solubility Product constant of the salt, Ksp(m)=4s3 f±<br />3 was calculated .On the other hand we concluded<br />the equilibrium constant of ion pair formation , KIP, on the basis of Fuoss contact ion pair model and<br />we obtained the value of ion pair concentration in the mixed solvents, (water 85% +ethanol l5% +<br />propanol 10%). The value of thermodynamic solubility product constant, Ksp(th), of CdF2 in the mixed<br />solvent was evaluated at zero ionic strength upon the extrapolation method and the value of ion pair<br />concentration was calculated in the considered solution and compared by fuoss model.