STRUCTURE OF THE IMMEDIATE ENVIRONMENT OF IONS IN ZINC CHLORIDE AQUEOUS SOLUTIONS ACCORDING TO XRD DATA

Abstract

Quantitative characteristics of the immediate environment of ions in aqueous ZnCl₂ solutions are determined by XRD in a wide range of concentrations. In a saturated solution, the Zn²⁺ ion coordinates two water molecules at a distance of 0.208 nm. The ions form an associate containing one Cl^– ion at a distance of 0.225 nm and two Cl^– ions at a distance of 0.380 nm. As the concentration decreases, the Cl^– ions leave the associate, starting with more distant ions and proceeding with the ion of the contact ion pair. As a result, the ion pairs are destroyed and Zn²⁺ and Cl^– ions undergo independent hydration. The number of water molecules in the coordination sphere of Zn²⁺ ions increases up to six within a distance of 0.212 nm. Dilution naturally increases the number of water molecules in the anion′s hydration sphere at an average distance of 0.312 nm and in the cation′s second coordination sphere at an average distance of 0.424 nm.