Thermodynamic Study of the NaCl–CuCl2–H2O Ternary System at 298.15 K by the Electromotive Force Method

In this work, we investigated some thermodynamic properties of the NaCl–CuCl2–H2O ternary system. We designed a cell without liquid junction as follows: Na-ISE | NaCl (m1), CuCl2(m2) | Cl-ISE, which was used to study the mean activity coefficients of NaCl in the NaCl–CuCl2–H2O system at 298.15 K by the electromotive force method. In this system, the total ionic strength Iranges from 0.01 up to 1.00 mol·kg–1for different ionic strength fractions ybof CuCl2, i.e., yb= (0.0, 0.2, 0.4, 0.6, 0.8). The results show that the Na-ISE and Cl-ISE have a good Nernst effect. The mean activity coefficients of NaCl in the ternary system were calculated using the Nernst equation. The Pitzer ion interaction parameters θNa,Cuand ψNa,Cu,Clwere fitted by Pitzer model with experimental results in this work. In addition, the osmotic coefficients, the solvent activities, and the excess Gibbs free energies of the ternary system were also calculated.