Density, speed of sound, and electrical conductance of ionic liquid 1-hexyl-3-methyl-imidazolium bromide in water at different temperatures

Densities, speeds of sound, and electrical conductances in the aqueous solutions of room temperature ionic liquid, 1-hexyl-3-methyl-imidazolium bromide, [HMIm]Br were measured at temperatures T = (283.15 to 308.15) K and atmospheric pressure. Apparent molar volumes Vϕ, isentropic compressibilities κS, apparent molar isentropic compressibilities κϕ, and molar conductivities Λ were determined. The corresponding limiting apparent molar quantities were found by extrapolation to infinite dilution with using Redlich–Mayer equation. The obtained limiting apparent molar quantities at different temperatures indicate that (ion + solvent) interactions in the studied system. Limiting apparent molar expansibility Eϕ∘ values for aqueous solutions of this ionic liquid have a positive values. The value of (∂2Vϕ∘/∂T2)P was found small and negative which indicating the ionic liquid under study is predominantly a structure breaker. Isentropic compressibility isotherms intersect approximately at a concentration m = 1.5825 mol · kg−1, which may be an indication of the structural interactions and clathrate formation. Calculated ion association constant Ka values increase with increasing temperature show that the extent of ion association increases with increasing temperature.