Microstructure and species distribution of aqueous zinc chloride solutions: results from Monte Carlo simulations
Abstract
Monte Carlo simulation results are reported for 1–5 mol kg–1 aqueous zinc chloride solutions and compared to experimental data. The structural data from the simulations indicate the formation of ZnCl(2–n)–n complexes with nmax= 2, in contrast to the stronger CuCl(2–n)–n complexes observed up to n= 4. Besides these ‘contact ion pair’ complexes, solvent-separated (‘outer-sphere’) complexes are found, co-determining the physico-chemical properties of ZnCl2 solutions. Formation constants for the ZnCl+ and ZnCl2 species could be evaluated from the simulations. Structural details of the complexes are visualized by ligand distribution plots, showing a breakdown of the order of the hydration structure at salt concentrations of ca. 5 mol kg–1, and a trans-conformation of the species ZnCl2(H2O)4.