A Study of Some Excess Thermodynamic Properties in Binary Mixtures of Non- Aqueous Solvents at Variable Temperatures

Excess thermodynamic properties, such as viscosity deviation (lnΔƞ), excess isentropic compressibility (Ks E), excess molar volume (Vm E), excess intermolecular free length (Lf E), excess free volume (Vf E), excess acoustic impedance (ZE), and excess internal pressure (Πi E), were calculated from the experimentally measured values of density (ρ), ultrasonic velocity (u), and viscosity (ƞ) for the binary mixtures of acetonitrile (AN) with dimethyl sulfoxide (DMSO) and N, N-dimethylacetamide (DMA) as a function of mole fraction at temperatures 298 K, 308 K, 318 K, and 328 K. The excess values were further fitted to Redlich-Kister polynomial equation to ascertain the fitting parameters and standard deviations. The variations of excess parameters with composition and temperature were further discussed with regard to the nature and extent of molecular interactions among the dissimilar component molecules of the investigated solvent systems. The analysis of these excess parameters revealed the presence of strong interactions between the components of the investigated binary mixtures. Overall, the positive deviation in ZE values and negative deviations in Lf E, Vf E, and Ks E values over the entire solvent composition range suggested the existence of strong molecular interactions between dissimilar molecules of the components. Compared to AN-DMSO solvent system, the AN-DMA solvent system exhibited more deviation towards a stronger interaction mode.