(262f) H3O+Cl- Pair Association In Highly Compressible Aqueous Environments. Simulation Results, Modeling Conjectures, And Experiment

An extensive molecular-based simulation effort to analyze ion-pairing behavior in near-critical dilute HCl aqueous solutions is performed along near-critical isotherms over a wide density range, i.e., from steam-like to liquid-like environments (*). The study encompasses the determination of the ion-pair association constant via potential of mean force calculations and the resulting degree of ion-pair association. The main goal behind this effort is to address a few relevant questions regarding the thermodynamic and corresponding microscopic behavior of the ion-pair formation in steam-like and highly compressible environments, where experimental data are extremely difficult to obtain accurately, to illustrate the ?uneventful' behavior of the association constant along the critical isotherm of the solvent, and to shed light into the hydration power of steam. Direct comparison is made between simulation, theoretical developments and experiment to identify potential pitfalls in the interpretation of experimental data and subsequent macroscopic modeling.

(*) A. A. Chialvo and J.M. Simonson. Journal of Physical Chemistry B (K. E. Gubbins' Festschrift) Submitted, April 2007.