Thermophysical properties of 1-butyl-3-methylimidazolium tetrafluoroborate and N-methyl-2-pyrrolidinone as a function of temperature

Abstract

Speed of sound (u), density (ρ) and refractive index (nD) values are measured for the binary mixture of 1-butyl-3-methylimidazolium tetrafluoroborate and N-methyl-2-pyrrolidinone over the entire range of mole fraction at temperatures from 298.15 to 323.15K. Using the basic experimental data, isentropic compressibility (κs), intermolecular free length (Lf), molar volume (Vm), molar refraction (Rm) and excess isentropic compressibility (κsE), excess intermolecular free length (LfE), and excess molar volume (VmE) values are calculated. The calculated properties are discussed in terms of molecular interactions between the present investigated binary mixtures. The excess values are fitted to Redlich–Kister polynomial equation to estimate the binary coefficients and standard deviation between the experimental and calculated values. Further, the molecular interactions in the binary mixture system are analysed using the experimental FT-IR spectrum recorded at room temperature.