The Electromotive Force Method Was Used To Study The Thermodynamic Properties Of Antimony Halide And Antimony Halide In Ethylene Carbonate-water Mixed System

Electrolyte solutions are the subjects in many research fields. The thermodynamic properties of electrolyte solution can reflect the ion-ion and ion-solvent interactions. As an extension of our research group on thermodynamic properties of the Rb and Cs salts, this paper has studied the thermodynamic properties of RbX/CsX （X=F, Cl, Br）-EC-H₂O systems at T=298.15 K.Part Ⅰ:phase chemistry. To maintain the homogeneous condition of the systems during potentiometric measurement, the solid-liquid phase equilibrium and liquid-liquid equilibrium of RbX/CsX （X=F, Cl, Br）-EC-H₂O systems were measured and discussed in detail. The four parameter equation was used to fit the solid-liquid equilibrium data. The three parameter equation （for binodal curves data） and Othmer-Tobias and Bancroft equations （for tie line data） were used to correlate the liquid-liquid equilibrium. Satisfactory correlation results were obtained.Part Ⅱ:electrochemistry. The ion-selective electrode Rb-ISE/Cs-ISE and the F-ISE/Br-ISE/Ag-AgCl electrode are selected as the anode and cathode to compose the galvanic cells without liquid junction:Rb-ISE| RbX, H₂O| F-ISERb-ISE| RbX, EC, H₂O| F-ISEThe electromotive force of RbX/CsX （X=F, Cl, Br） in EC-H₂O mixtures was obtained by potentiometric method at T=298.15 K. The Nernst equation together with Pitzer, the modified Pitzer and the extended Debye-Hiickel equations are applied to process the measured data. The activity coefficient γ±, osmotic coefficient 0, excess Gibbs free energies G^E, the standard free energy of transference △G_t⁰ of the systems and the standard solubility product　lnK_sp,m⁰ were also calculated.