Apparent molar properties of hydroxyethyl ammonium based ionic liquids with water and ethanol at various temperatures

Abstract The density, ρ and speed of sound, u data for binary solutions of protic ionic liquids (PILs) namely N-butyl-2-hydroxyethyl ammonium formate (BHEAF) and N-butyl-2-hydroxyethyl ammonium acetate (BHEAAc) with water and ethanol, as a function of molality, m ranging from (0.1 to 0.8) mol.kg − 1 were measured from (293.15 to 318.15) K under 0.1 MPa pressure. The apparent molar volume, V ϕ apparent molar isentropic compressibility, K s,ϕ and limiting apparent molar expansion, E ϕ ∞ have been determined from experimental density and speed of sound data. The apparent molar volume, V ϕ ∞ and apparent molar isentropic compressibility, K ϕ ∞ at infinite dilution and corresponding empirical parameters ( S v , B v , S k and B k ) were calculated by using the Redlich–Mayer equation. The calculated V ϕ ∞ and K ϕ ∞ values indicate that ILs–ethanol interactions are stronger than ILs–water interactions. Further, thermodynamic properties of binary mixtures were explained on the basis of the influence of the anion structural contribution of protic ionic liquids.