Conductometric Studies of 1-Ethyl-3-methylimidazolium Tetrafluoroborate and 1-Butyl-3-methylimidazolium Tetrafluoroborate in N,N-Dimethylformamide at Temperatures from (283.15 to 318.15) K

The electrical conductances of dilute solutions of the ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate [emim]BF4 and 1-butyl-3-methylimidazolium tetrafluoroborate [bmim]BF4 in N,N-dimethylformamide have been measured over the temperature range from (283.15 to 318.15) K. The ionic association constant, K-A, limiting molar conductivities, Lambda(o), and distance parameters, R, were obtained using the Fuoss-Justice equation for the investigated systems. Slight ion association effect was found for the ionic liquids in DMF at all experimental temperatures. From the temperature dependence of the limiting molar conductivities the Eyring's activation enthalpy of charge transport was estimated. The thermodynamic functions such as Gibbs free energy, entropy, and enthalpy for the process of ion pair formation were calculated from the temperature dependence of the ion association constants.