Thermodynamics of molecular interactions in ethyl iodide–xylene mixtures

Abstract

The excess Gibbs free energies of mixing, G^E, for ethyl iodide plus o-, m- and p-xylene at 298.15 K have been obtained from the measured vapour-pressure data. The G^E values for ethyl iodide—m-xylene are positive while those of p- and o-xylene are negative throughout the ethyl iodide concentration range. The results have been analysed in the terms of Flory, Sanchez and Lacombe and an ideal associated model theory of non-electrolyte solutions. It has been observed that the ideal associated model approach, which assumes the presence of AB and A₂B molecular species, describes well (within ± 10 J mol^–1 at the most) the general dependence of H^E on x_A(mole fraction of ethyl iodide) over the whole composition range for ethyl iodide and xylene mixtures. The equilibrium constants for the reactions A + B ⇌ AB and 2A + B ⇌ A₂B along with the enthalpies of formation of the molecular species AB and A₂B have also been calculated.