Single-ion enthalpies and entropies of transfer from water to aqueous urea solutions at 298.15 K

Abstract

In this paper we report enthalpies of solution at infinite dilution [Formula: see text] at 298.15 K for tetraphenylarsonium chloride (Ph4AsCl), sodium tetraphenylborate (NaBPh4), sodium chloride (NaCl), sodium bromide (NaBr), and sodium iodide (NaI) in water and aqueous solutions containing 5, 10, 20, and 30% urea by weight. Enthalpies of transfer from water to aqueous urea solutions are reported. Single-ion enthalpies of transfer [Formula: see text] have been calculated using the tetraphenylarsonium tetraphenylborate, (TATB) reference electrolyte assumption. These single-ion enthalpy data have been combined with single-ion Gibbs functions of transfer [Formula: see text] reported in the literature to obtain single-ion entropies of transfer [Formula: see text] for the urea + water mixed solvent system. The results of this single-ion analysis are discussed in terms of the impact of electrolytes on the structure of aqueous urea solutions.