The osmotic and activity coefficients and vapor pressures of binary mixtures containing the alcohols 1-propanol, 2-propanol, 1-butanol, 2-butanol and 1-pentanol and the ionic liquid 1-hexy13-methylimidazolium bis(trifluoromethylsulfonyl)imide, C(6)MimNTf(2), were determined at T=323.15 K using the vapor pressure osmometry technique. The experimental osmotic coefficients were correlated using the Extended Pitzer model of Archer and the MNRTL model, obtaining standard deviations lower than 0.020 and 0.049, respectively. The mean molal activity coefficients and the excess Gibbs free energy for the studied mixtures were calculated from the parameters of the Extended Pitzer model of Archer. Besides the effect of the alkyl-chain of the alcohol and the position of the alcohol group, the effect of the alkyl-side chain of the cation of the ionic liquid can be assessed comparing the experimental results with those previously obtained for imidazolium bis(trifluoromethylsulfonyl)imide ionic liquids with different alkyl-side chain lengths. (C) 2011 Elsevier B.V. All rights reserved.