Viscometric Studies of Ion Solvation of Some Alkali Metal Salts in 2-Aminoethanol + N,N-Dimethylacetamide Binary Mixtures at 298.15 K and 308.15 K

Abstract

Densities (ρ) and viscosities (η) of lithium perchlorate (LiClO4), sodium perchlorate (NaClO4), potassium thiocyanate (KSCN), tetrabutyl-ammonium thiocyanate (Bu4NSCN), tetrabutylammonium tetraphenylborate (Bu4NBPh4) and tetrabutylammonium perchlorate (Bu4NClO4) were measured in binary mixed solutions of 2-aminoethanol (AE) and N,N-dimethylacetamide (DMA) containing 25, 50, 60, 80 and 100 mol % DMA in the concentration range (3-500) ×10-4 mol kg-1 at 298.15 K and 308.15 K temperatures. The density and viscosity data were analyzed using the Jones-Dole equation in the form ηr = 1 + A(C1/2) + BC for unassociated electrolytes and viscosity A and B-coefficients were obtained from the plots of of ηr – 1/C1/2 versus C1/2. The A-coefficients obtained from the analysis of Jones-Dole equation are positive as well as negative. The positive values indicate the solvation of ions in solutions of binary mixtures (AE + DMA) especially in 50 and 60 mol% DMA. The viscosity B-coefficients of all these electrolytes were positive and large in case of cations and were split into their respective ionic (B±) coefficient values using a method reported by Gill and Sharma. The viscosity B-coefficients values were increasing with the increase increasing DMA composition in the binary mixed solvent system of AE + DMA but decreasing with increasing temperature from 298.15 K to 308.15 K. The obtained results indicate about the preferential solvation of ions i.e. Li+, Na+, K+, Bu4N+ and Ph4B– ions and poor solvation of ClO4 – and SCN– ions. The results also revealed that these interactions get weaker with increase in temperature. The resulting B-coefficients and its dependence of temperature provide useful information regarding changes in the solvent structure.