Thermodynamic modeling of NaCl+RbCl electrolytes in water-Ethanol solvent mixtures based on the electrochemical data and the Pitzer theory

The knowledge of the thermodynamic properties of mixed solvent mixed electrolyte solution are needed for understanding the nature of various ionic interactions andcontrolling many industrial and environmental process. As we know, rubidium and its salts are rare in the world and cannot form mineral salts because they are extremelyreactive. Also, due to its high price, the market for these compounds is very small; so, there is less thermodynamic data for this metal and its salts than other alkali metals and related compounds. Studies on this metal and its salts showed that they have applications like night-vision equipment, batteries, fiber optic telecommunication systems and an ingredient of metal-ion catalysts [1]. in this research, we showed the thermodynamic properties of NaCl+RbCl+H2O+C2H5OH at 298.15 K. A galvanic cell without a liquid junction containing a Na+-glass membrane and Ag/AgCl electrodes were used along with a computerized data acquisition system for collecting the potentiometric experimental data over the ionic strength ranging from 5.10-4 and up to about 4 mol/kg at 298.15 K. Different theoretical electrolyte models were used for investigation of these electrolytic systems. The use of the Pitzer model permitted the determination of parameters ( (1) (0) C , ,    ) for single salts and mixing ion-interaction ( , ijk ij   )parameters for these investigated systems[2]. The interaction parameters obtained for this system and the graph of the values of the experimental mean activity coefficients in different mass percentages of Ethanol in water are given below.