Vapor heat capacities of some polar–polar binary systems

Abstract

The calorimetric results of isobaric vapor heat capacities are presented by using a constant-flow calorimeter for five polar–polar binary systems, acetone–butanone and chloroform–ethyl acetate at 402.2 K, ethanol–methanol, ethanol– n-propanol and ethanol– n-butanol at 402.2 and 441.3 K, with respect to compositions at atmospheric pressure. The residual heat capacities and the excess heat capacities of the mixtures are calculated. Relatively significant values of the residual heat capacity are observed even at atmospheric pressure in these polar–polar binary systems. The excess vapor heat capacities of acetone–butanone system are nearly zero, but those of other polar–polar systems have relatively large positive values. These results are discussed under the consideration of the changes of the intermolecular forces. Furthermore, two well-known generalized equations of state are chosen for the estimation of the vapor heat capacities of these binary mixtures. Comparison between the calculated and the experimental results indicates that the two equations of state may be used to the vapor heat capacity estimation near atmospheric pressure even for polar systems.