Vapor-liquid equilibrium of aqueous [C6H11N2][HSO4] and LiBr systems and the ternary ([C6H11N2] [HSO4 + LiBr + H2O) system are studied at T = 298.15 K. Isopiestic method applied to obtain the water activity, osmotic coefficient, activity coefficient and vapor pressure. For binary mixtures, the different models such as Pitzer, Pitzer - Archer and Modified-Pitzer models are fitted to the osmotic coefficients data, and for the studied ternary system, we used the Scatchard's natural electrolyte model to correlate the osmotic coefficients values at T = 298.15 K. The effect of [C6H11N2][HSO4] on volumetric properties of aqueous LiBr solutions is considered. Limiting apparent molar expansibilities are obtained and McMillan-Meyer parameters are evaluated. (C) 2016 Elsevier B.V. All rights reserved.