Quaternary System Thermodynamic Investigation in a Mixed Solvent: NaCl + KCl + N,N-Dimethylformamide + H₂O

Abstract

This article focuses on measuring and modeling activity coefficients and some thermodynamic properties of the quaternary system (NaCl + KCl + N,N-dimethylformamide (DMF) + H 2 O) using a potentiometric technique at (298.15 ± 0.05) K. By employing ion-selective electrodes (Na + -ISE, Cl − -ISE), experimental results were collated for the four series of the mixed electrolyte systems in various ionic strengths for the investigated quaternary system. The electrochemical measurements were carried out over total ionic strengths range from 0.0249 up to about 3.8223 mol•kg −1 in mixed N,N-dimethylformamide + H 2 O solvents, with various solvent mass percents (wt % = 0.0, 0.10, 0.20, and 0.30) at 298.15 ± 0.05 K. Experimental data were modeled on the basis of the Pitzer approach, and the two and three particles mixing ionic interaction parameters (θ NaK and ψ NaKCl ) estimated for the quaternary electrolyte systems under investigation. Finally, using the optimized parameters (θ NaK and ψ NaKCl ), the thermodynamic properties of electrolyte systems, such as activity coefficients of the constituent's electrolyte, osmotic coefficients, and the excess Gibbs free energy, were determined for each mass percent of DMF in water for mixtures of sodium and potassium salts with common anion chloride. The resultant activity coefficients demonstrate a decreasing trend upon decreasing dielectric constants and as the mixed solvent medium growing dense and viscous.

Thermodynamic Study of Binary Sodium Chloride and Rubidium Chloride in Mixed Methanol–Water Employing the EMF Method

“…Additionally, Figure displays that activity coefficients of NaCl initially decreased with an increase in the values of ionic strength under study and then almost remained stable within the molalities restricted by electrolyte solubility. Upon increasing the weight percent of cosolvent, these activity coefficients show decreasing trends and are in satisfactory agreement with the similar systems with DMF as cosolvent . It should be mentioned that the values of m R (molality of the reference) were arbitrary and taken to be approximately 0.99 mol.…”

“…27−41 Our group has lately made use of the potentiometric method and Pitzer ion interaction and the modified Pitzer approaches to determine and describe the interactions between nonelectrolyte (amide, carbohydrate, and alcohols) and inorganic salts in multicomponent solutions, namely, the ternary and quaternary systems of mixed electrolytes (NaCl+KCl) in mixed solvents (such as N,N-dimethylformamide + water) and in aqueous alcohol solutions. 36,40,41 As continuation of our studies on the binary mixed electrolytes in binary mixed solvents, a survey of literature indicates that the thermodynamic data of mixed salts of sodium and rubidium chlorides in a mixed CH 3 OH + H 2 O system have not been reported to date. Taking into account the considerations quoted above, the main objective of this study is the measuring and modeling of the activity coefficients of the electrolytes and subsequently osmotic coefficients and Gibbs free energies in a quaternary system (NaCl + RbCl + CH 3 OH + H 2 O) by using the electromotive force measurement technique.…”

“…Upon increasing the weight percent of cosolvent, these activity coefficients show decreasing trends and are in satisfactory agreement with the similar systems with DMF as cosolvent. 36 It should be mentioned that the values of m R (molality of the reference) were arbitrary and taken to be approximately 0.99 mol.…”

“…Lastly, Figure 6 shows the decreasing trend for the excess Gibbs free energy against total molalities; this trend is ordinarily for exergonic systems and is in the same manner as can be seen in references for the nearly similar systems in other alcohols. 36,40 According to Gurney's framework, the electrolyte composed of ions with the same solvent structure classification such as chloride and rubidium are termed as chaotropic but sodium is less chaotropic and hence the plot of activity coefficients at higher concentrations has a low-lying behavior for NaCl and a high-lying behavior for RbCl (see Figures 2 and 3). 37 Correspondingly, a systematic and comparative study of the thermodynamic behavior of the systems of type NaCl + MCl with M = Li, K, Cs was performed by Holmes et al, 16 in which they have shown that the most structure-breaking cation (M) gives rise to the wider interval of activity coefficients for the first electrolyte upon increasing total molalities; surprisingly, the data of Table 4 and Figure 2 of the present study are in line with their findings.…”

“…In the course of various methods for thermodynamic study of the analogous quaternary system, when nonelectrolyte is liquid, no more tool except for EMF made it plausible to evaluate the activity coefficients and subsequent thermodynamic quantities. − Our group has lately made use of the potentiometric method and Pitzer ion interaction and the modified Pitzer approaches to determine and describe the interactions between nonelectrolyte (amide, carbohydrate, and alcohols) and inorganic salts in multicomponent solutions, namely, the ternary and quaternary systems of mixed electrolytes (NaCl+KCl) in mixed solvents (such as N , N -dimethylformamide + water) and in aqueous alcohol solutions. ,, …”