Solvation Behaviour of Ions in N,N'-Dimethyl Formamide-Water Mixtures Between 298 and 313 K from Thermodynamic Parameters of Viscous Flow

Abstract

Viscosity B-coefficients of Jones-Dole equation for the halides of potassium
in dimethyl formamide-water mixtures have been utilised to evaluate
the thermodynamic parameters of viscous flow between the temperature
range 298 and 313 K, using the method of Nightingale and Benck. Ionic
Viscosity B-coefficient as well as ionic thermodynamic parameters of viscous
flow are obtained on the basis of the concept that the influence of
potassium ion upon the viscous flow phenomenon in DMF-H₂O mixtures
is approximately equal to that for chloride ion. These ionic data together
with their variation with temperature and mole-fraction of DMF in solvent
are utilised in understanding qualitatively the ion-solvent interaction.
ΔE* ion and ΔS* ion values are found to decrease with temperature as
well as mole-fraction of DMF in solvent for halides and monovalent
Na⁺ ion and K⁺ ion. In case of divalent Ca²⁺, Sr²⁺ and Ba²⁺ ions, ΔS*
ions are found to increase with rise of temperature. Ionic activation energy
and ionic activation entropy of viscous flow at studied temperatures
decreases in the order of Na ⁺ > K⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺ for cations and
r^-> Br^- > Cl^- for anions.