Experimental activity coefficients of different alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and 1-pentanol) and ketones (acetone, 2-butanone, 2-pentanone, 3-methyl-2-butanone and 4-methyl-2-pentanone) at infinite dilution in 1-Ethyl 3-Methylpyridinium Ethyl Sulfate ionic liquid (IEMpyl[ESO4]) were measured at temperatures from 323 to 373 K, using the inverse gas chromatography technique. The experimental results show that infinite dilution activity coefficients of both alcohols and ketones only marginally depend on temperature between 323 and 373 K. Further, it could be observed that infinite dilution activity coefficients of methanol, ethanol, and 1-propanol are lower than unity, whereas 1-butanol and 1-pentanol activity coefficients at infinite dilution were higher than unity. In contrast, the activity coefficients at infinite dilution of all ketones were found to be greater than unity. Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was used to model the obtained experimental data. Firstly, the pure-component parameters for [EMpy][ESO4] were determined by fitting experimental pure-IL densities and activity coefficients of 1-propanol. Based on this, activity coefficients in binary [EMpy][ESO4]/alcohol and [EMpy][ESO4]/ketone mixtures were modeled with good agreement to experimental data. Binary interaction parameters between [EMpy][ESO4]/alcohol and [EMpy][ESO4]/ketone were used. They were found to depend logarithmically on the chain length of any alcohol or ketone, respectively. (C) 2015 Elsevier B.V. All rights reserved.