KCl / RbCl / CsCl In DMA / NMF / Urea + H _{Thermodynamic Properties 2} O In

The thermodynamic properties of alkali metals are widely used in industrial production and our daily life. On the other hand, as one of the model compound of protein, amide solution has also been extensively investigated. The study of thermodynamic properties of KCl/RbCl/CsCl in amide-water mixed solvent became an important part of solution chemistry.In this work, the thermodynamic properties of ternary systems of KCl/RbCl/CsCl in N, N-dimethylacetamide (DMA)/N-methylformamide (NMF)/urea+H2O were investigated using the potentiometric measurements. The ion-selective electrode (K-ISE/Rb-ISE/Cs-ISE)and the Ag-AgCl electrode worked as the anode and cathode, respectively. The galvanic cells without liquid junction are as follows:K/Rb/Cs-ISE|KCl/RbCl/CsCl(m), DMA/NMF/urea (w), water(1-w)|Ag-AgCl m stands for the molality of MCl (M=K, Rb, Cs) solution. w is the mass fraction of DMA/NMF/urea in the mixtures(10%,20%and30%).The electromotive forces of these systems were determined and fitted to the Nernst equation and the Pitzer model. The mean activity coefficients, osmotic coefficients, solubility product, the standard free energy of transfer and the model parametershas been achieved. The modified Pitzer model and the extended Debye-Huckel model were also used to verify the experimental data. It should be noted that the calculated results by these three models show a good agreement. The mean activity coefficients decrease with the increasing of the concentration of the electrolyte when the mass fraction of solvent is constant.One the other hand, these coefficients increase with the decreasing of the mass fraction of solvent when the concentration of salt is changeless. The osmotic coefficients show a trend as the activity coefficients. The standard free energy of transference and the solubility product of KCl/RbCl/CsCl in the mixed solvent were furtherly calculated with the standard Gibbs energies and the solubility product in pure water.