Thermodynamic properties of the benzene and cyclopentane system

Abstract

Total vapour pressure data have been obtained for the system benzene + cyclopentane at 25, 35 and 45°C. These data, along with volumetric data for the pure liquids and calculations of gas-phase properties for the mixtures, were reduced to excess free energies of mixing using the method of Barker. The excess free energies of this system are nearly symmetrical in mole fraction; at 35°C the excess free energy of the equimolar mixture is 65·0 cal/g mole. However, this system does not form regular solutions; the product of the temperature and the excess entropy of mixing at constant pressure is 64·3 cal/g mole for the equimolar mixture at 35°C. Calculations of the excess functions at constant volume were made using the equations of Scatchard and the excess volume data of Klapproth. These calculations show that, contrary to the refined Hildebrand theory of solutions of nonpolar molecules, the excess entropy is far from negligible even if corrections are made for the observed volumetric expansion which accompanies the solution process.