Thermochemical properties of electrolyte solutions in {2-(2-methoxyethoxy)ethanol + water} and (2-isopropoxyethanol + water) mixtures at 298.15 K

Dissolution enthalpies of NaCl and NaI in aqueous solution of 2-(2-methoxyethoxy)ethanol (C1E2) and 2-isopropoxyethanol (iC3E1) have been measured and appropriate enthalpic pair interaction coefficients, hxy (electrolyte-non-electrolyte), in water have been determined at 298.15 K. Our investigations are a continuation of earlier studies concerning the influence of the alkyl group size in the 2-alkoxyethanol (2-methoxyethanol, 2-ethoxyethanol or 2-butoxyethanol) molecule on solution properties. The standard solution enthalpies, ΔsolHm∞ of the salts in all the investigated systems pass through a maximum in the water-rich region. The presented maxima appear to be a result of the endothermic effect of the destruction of the 2-alkoxyethanol molecules hydration shell and the exothermic effect of replacement of water molecules by cellosolve ones in ionic solvation shells. The position and height of the maximum depend both on the nature of the salt and of the 2-alkoxyethanol molecule. The hxy values are positive for all the systems investigated here. It indicates that in the infinitely diluted aqueous solution, the endothermic effect resulting from the destruction of the hydrophobic cage around the 2-alkoxyethanol molecule predominates over the exothermic effect of the electrostatic ion-cellosolve interaction