Ion association and solvation characteristics of Li+, Na+ and K+ ions in binary mixtures of 2-Aminoethanol + N,N-Dimethylacetamide probed by conductometry study at 298.15 K and 308.15 K

Abstract

Molar conductances (Λ) of LiClO₄, NaClO₄, KSCN, Bu₄NSCN, Bu₄NClO₄ and Bu₄NBPh₄ in binary solvent mixtures of 2-aminoethanol (AE) and N,N-dimethylacetamide (DMA) containing 25, 50, 60, 80 and 100 mol% DMA have been measured at 298.15 K and 308.15 K in the concentration range of (30-500) × 10^-3 mol kg^-1. The conductance data of the electrolytes in the binary mixtures of AE+DMA are analyzed using Shedlovsky’s equation to evaluate limiting molar conductances (Λ_o), association constants (K_A), Walden products (Λ_oη_o), hydrodynamic radii (R_H) and the standard free energies of association (∆G_A⁰). The individual limiting ionic molar conductances are obtained using the reference electrolyte tetrabutylammonium perchlorate (Bu₄NClO₄) and tetrabutylammonium tetraphenylborate (Bu₄NBPh₄). A modified form of Stokes’ law helped to determine the solvated ionic radii (r_i) in solutions and are assessed in the facet of ion-ion, ion-solvent interactions and show structural changes in the binary mixtures. The results has revealed that the solvated radii (r_i) values of Li⁺, Na⁺ and K⁺ ions show preferential solvation of these ions by DMA in AE+DMA binary mixtures and these interactions get weaker with the increase in temperature. Also, the preferential solvation and ion-solvent interactions of these ions in binary mixtures are proved by the analysis of Walden products (Λ_oη_o) and the standard free energies of association (∆G_A⁰) with the effect of temperature.