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Osmotic coefficients, φ, electrical conductance data, Λ, and refractive indices, n D , of aqueous solutions of the ionic liquid, 1-pentyl-3-methylimidazolium chloride [PnMIm]Cl have been measured at T = (298. 15, 308.15, 318.15, and 328.15) K. Measurements of osmotic coefficients were carried out by the vaporpressure osmometry method (VPO). Osmotic coefficient values show that ion-solvent interactions are stronger at lower temperature. The osmotic coefficients were correlated to the Pitzer-ion interaction and modified NRTL (MNRTL) models. From these data, mean molal activity coefficients, γ ±, and excess Gibbs free energies, G E , have been calculated. Electrical conductance data have been applied for determination of association constants, K a , and limiting molar conductances, Λ 0 , using the low concentration chemical model (lcCM). Calculated ion-association constant, K a , values show that ion-association effects increase at high temperatures which is in agreement with osmotic coefficient results. Experimental results of refractive indices for the binary system are reported, and have been fitted by a polynomial expansion.

Experimental results of the osmotic coefficients and refractive indices of aqueous solutions of ionic liquids containing 1-butyl-3-methylimidazolium chloride, [BMIm]Cl, and 1-butyl-3-methylimidazolium iodide, [BMIm]I, have been measured over the composition range of 3 mol • kg -1 at T ) (298.15 to 328.15) K. The determination of experimental osmotic coefficients was performed by the vapor pressure osmometry method. The results show that osmotic coefficients increase when the concentration of ionic liquid and temperature increase. The osmotic coefficients were correlated to the Pitzer ion interaction and modified NRTL (MNRTL) models. From these data, mean activity coefficients and excess Gibbs free energies have been calculated. The results have been interpreted in terms of ion-solvent and ion-ion interactions and structural factors of the ionic liquid. Experimental results of refractive indices for the binary system are reported and have been fitted by a polynomial expansion.

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