Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

Using thermogravimetrical analysis, the enthalpies of vaporization at an average temperature, Dg lHo m(Tav), for ionic liquids (ILs) {1-alkyl-2,3-dimethyimidazolium-N,N-bis(trifluoromethyl sulfonyl)imide} [CnDmim] [NTF2] (n = 2, 4) were firstly determined and transformed into Dg lHo m(298 K) based on the Dg lCp o m. Then, on the basis of Tong s vaporization enthalpy model, a new thermodynamic quantity-molar surface Gibbs free energy, g was put forward and the values of g were calculated for [CnDmim][NTF2] (n = 2, 4). In terms of the molar surface Gibbs free energy, a new Eotvos empirical equation was derived so that the new Eotvos parameters have clear physical meanings: its slope is molar surface entropy, s, and the intercept is the molar surface enthalpy, h, the value of which is not change with temperature. Moreover, the values of molar surface Gibbs free energy can be estimated using the b and Tc easily, according to the new Eotvos equation and g = N1/3cV2/3, the surface tensions for [CnDmim][NTF2] (n = 2, 4) and other ILs could be predicted, and the predicted values were in good agreement with the experimental values.