Specific Features of Motion of Cations and Anions in Electrolyte Solutions

TL;DR

This study investigates ion and water molecule mobility in dilute electrolyte solutions, revealing that their behavior is primarily influenced by hard shell radii rather than hydrogen bonding, with specific insights into potassium and fluoride ions.

Contribution

It demonstrates that ion and water mobility are governed by hard shell radii and provides microscopic explanations for differences in cation and anion behavior using the Stillinger--David potential.

Findings

Mobility coefficients depend on hard shell radii.

Hydration effects minimally impact density and diffusion.

Distinct behaviors of K+ and F- ions explained by intermolecular interactions.

Abstract

The nature of mobility of ions and water molecules in dilute aqueous solutions of electrolytes (at most fifteen water molecules per ion) is investigated. It is shown that the behavior of the mobility coefficients of water molecules and ions, as well as the self-diffusion coefficients of water molecules, are determined by the radii of their hard shells rather than by the effect of the hydrogen bond network. It is established that the influence of hydration effects on the density of the system and the self-diffusion coefficients of water molecules does not exceed several per cent. Based on microscopic concepts, it is shown that the different behaviors of a $\rm K^{+}$ cation and an $\rm F^{-}$ anion with equal rigid radii are in good agreement with specific features of the intermolecular interaction described by the generalized Stillinger--David potential.