Thermodynamic properties of (KCl/KSCN/H۲O) ternary electrolytesolution by potentiometric method at T=۲۹۸.۱۵ ± ۰.۱ K

In this study, the thermodynamic properties of three-component electrolyte solution (KCl + KSCN +H۲O) were investigated. For this purpose, first the mean activity coefficients of KCL as the maincomponent were determined by potentiometric method. Potentiometric measurements were performed ina galvanic cell without liquid junction. In this galvanic cell, a polymeric membrane was used as thepotassium ion selective electrode and a silver-silver chloride electrode was used as the chloride ionselective electrode. The potentiometric measurements were performed at a temperature of ۲۷۳.۱۵ ± ۰.۱Kelvin in the total ionic strength range of solution between ۰.۰۰۱۷ to ۲.۰۰۰۰ mol kg-۱. The investigatedmolal ratios of the two salts in the solution were r =mkcl/mkscn== ۱.۰, ۲.۵, ۵.۰, ۱۰.۰, ۱۵.۰ and pure KCl. ThePitzer ion interaction model and Harned rule were used to study the thermodynamics properties of thesolution. From the adaptation of the experimental mean activity coefficients of potassium chloride data inthe solution with the Pitzer ion interaction model, the mixing Pitzer parameters (θClSCN, ψKClSCN) weredetermined. Then these parameters were used to calculate the thermodynamic properties such as the meanactivity coefficients of potassium thiocyanate ( ), the osmotic coefficients of the solvent ( ) andthe Gibbs free energies of the solution (GE) based on the Pitzer ion interaction model. The Harandinteraction coefficients were obtained using the graph drawing method, too. The results showed that bothPitzer ion interaction model and Harned rule were successful in describing the experimental mean activitycoefficients results.

Keywords:

KCl , KSCN , Pitzer ion interaction model , Potentiometric method.Thermodynamicproperties , ,