The molar surface Gibbs free energy and its application for aqueous solutions of ionic liquid N-butyl-pyridinium dicyanamide [C4py][DCA]

Abstract

The values of density and surface tension for aqueous solutions of [C 4 py][DCA] were determined from 0.01000 to 0.5000 mol kg -1 at T = (288.15-318.15) K. The values of the molar volume for aqueous solutions of [C 4 py][DCA], V, were calculated and increase with the increase in temperature and molarity. On the basis of a new thermodynamic function-molar surface Gibbs free energy, g s , a semi-empirical model for the IL solutions is proposed. It can be used to predict the surface tension, and the predicted values of the surface tension for aqueous [C 4 py][DCA] are in good agreement with the corresponding experimental ones.In terms of the concept of the molar surface Gibbs free energy, a new Eötvös equation is obtained. Each parameter of the new Eötvös equation has a clear physical meaning, energy dimension: the absolute value of slope is the mole surface entropy, s, and intercept is the molar surface enthalpy, h, which is temperature-independent.