Thermodynamic properties of tetra-alkylammonium ions in aqueous solution

Abstract

The heat capacities of tetraethyl- and tetrapropyl-ammonium iodide have been measured in the temperature range 12–310 K. The solubilities of the two iodide salts have been determined at 298·15 K. and auxiliary data used to calculate values of 210 ± 3, 283 ± 4, and 336 ± 5 J K^–1 mol^–1 for the respective standard partial molar entropies of the ions NMe₄⁺(aq), NEt₄⁺(aq), and NPr₄⁺(aq), the value for the aqueous proton being taken as zero. Equations designed to reproduce the hydration energies of alkali and alkaline-earth metal ions are unsuitable for the tetra-alkylammonium ions.