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Conductometric studies of the physicochemical properties of selected ionic liquids in tetraethylene glycol in the temperature range T= (278.15 - 313.15) K

The electrical conductivity of diluted solutions of ionic liquids of 1-methylimidazolium chloride, 1, 3-dimethylimidazolium chloride, 1-ethyl-3- methylimidazolium chloride, and 1-butyl-3- methylimidazolium chloride in tetraethylene glycol was measured in the temperature range from 278.15 K to 313.15 K. The obtained conductivity results were analyzed with the use of a low concentration chemical model (lcCM) in order to determine the value of ionic association constant and the limiting molar conductivity. A slight ionic association was found for ionic liquids in tetraethylene glycol in the studied temperature range. From the limiting molar conductivity dependencies on temperature, the Eyring activation enthalpy values of the charge transfer were determined. Thermodynamic parameters such as Gibbs free energy, entropy, and enthalpy of ion pair formation were estimated from the values of association constants at various temperatures. The negative values of Gibbs free energy indicate that the formation of ion pairs is a spontaneous process. The increase in temperature leads to more negative values of Gibbs energy which means a shift of the equilibrium towards the formation of ion pairs. The obtained results were compared with those obtained for ethylene glycol.

ionic liquids ; tetraethylene glycol ; conductometry

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