CONICET | Buscador de Institutos y Recursos Humanos

We present an undergraduate laboratory experiment that allows a thermodynamic characterization of micelle formation of sodium dodecyl sulfate, SDS, in aqueous solutions. The Critical Micelle Concentration, CMC, and the degree of micelle ionization, a, are obtained at different temperatures by conductimetry. The molar standard free energy, enthalpy and entropy for the micellization process are calculated using the CMC, a, and their temperature dependences within the framework of a simplified model - the closed association model - that assumes equilibrium between free surfactant monomers and monodispersed micelles. Based on hydration phenomena of surfactant molecules, a physicochemical discussion of the results is also proposed.