Intermolecular interactions in binary mixtures of phosphonium based ionic liquid and propanoic acid

Thermophysical properties of binary systems containing trihexyltetradecylphosphonium chloride [P-14, 6, 6, 6(+)] [Cl-] ionic liquid (IL) and propanoic acid (PA), have been investigated. Measurements of densities (rho), and speeds of sound (u) have been made at p = 0.1 MPa and at varying temperatures ranging from 293.15 to 313.15 K. The computed excess properties which include excess molar volume (V-m(E)), apparent molar volume (V-phi), intermolecular free length (L-f), isentropic compressibility (k(s)), apparent molar isentropic compressibility (K-phi) and deviation in isentropic compressibility (Delta k(s)) have been computed from the experimental data of densities and speeds of sound. Based on the calculated derived properties, it is evident that the investigated IL and PA exhibit strong interactions across the entire mole fraction composition. Good correlation has been achieved with the Redlich-Kister equation.