Isobaric Heat Capacity of Ionic Liquids in Aqueous Solutions. A Review

A review of the available literature data for heat capacity of room temperature ionic liquid aqueous solutions is presented. To show at what extent their behavior departs from that of the ideal mixture, excess and apparent heat capacities are calculated. A comparison between different systems is made in order to elucidate the main factors that affect heat capacity behavior. The experimental results are also compared with available heat capacity data for salts and molecular compounds. Large deviations from ideality appear at low ionic liquid mole fraction. It is found that this nonideal behavior resembles, for most studied systems, that of molecular systems characterized by large hydrophobic domains. The appearance of pseudomicellar structures in diluted ionic liquid solutions seems to be the origin of the anomalies in the behavior of heat capacity.