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 (Λo), association constants (KA), Walden products (Λoηo), hydrodynamic radii (RH) and the standard free energies of association (ΔGA0). 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 (ri) 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 (ri) values of Li+, Na+ and K+ ionsshow 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 (Λoηo) and the standard free energies of association (ΔGA0) with the effect of temperature.