Conway / White Modern Aspects of Electrochemistry

1. Auflage 2006
ISBN: 978-0-306-47604-4
Verlag: Springer US
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, Band 35, 345 Seiten, eBook

Reihe: Modern Aspects of Electrochemistry

Recognized experts present incisive analyses of both fundamental and applied problems in this continuation of a highly acclaimed series. Topics in Number 35 include: Impedance spectroscopy with specific applications to electrode processes involving hydrogen; Fundamentals and contemporary applications of electroless metal deposition; The development of computational electrochemistry and its application to electrochemical kinetics; Analysis of electrolyte solutions at high concentrations; Applications of the Born theory to solvent polarization by ions and its extensions to treatment of kinetics of ionic reactions. £/LIST£

Zielgruppe

Research

Autoren/Hrsg.

Conway, Brian E.

White, Ralph E.

Inhaltsverzeichnis

Applications of Electrochemical Impedance Spectroscopy to Hydrogen Adsorption, Evolution and Absorption into Metals.- Electroless Deposition of Metals and Alloys.- Towards Computational Electrochemistry - a Kineticist’s Perspective.- Thermodynamic and Transport Properties of Bridging Electrolyte-Water Systems.- Factors Limiting Applications of the Historically Significant Born Equation: a Critical Review.

Leseproben

4 Thermodynamic and Transport Properties of Bridging Electrolyte-Water Systems (p. 197-198)

Maurice Abraham and Marie-Christine Abraham
Département de Chimie, Université de Montréal, Montréal, Canada

I. INTRODUCTION

For a long time, most efforts in the physical chemistry of solutions were made to obtain information on the structure of aqueous electrolytic solutions. But, at the same time as our knowledge of these solutions was expanding, especially regarding dilute solutions, another field of research attracted attention, the physical chemistry of molten salts, with increasing interest in new technologies. Due to various reasons of scientific, technological and even historical nature, most investigations in these two fields of research were made almost independently. According to Braunstein classification, 1,2 between dilute aqueous solutions and molten salts lie the hydrates, with complete or incomplete water shells around the ions, covering a very large water mole fraction range, from about 0 to 0.9. Obviously, investigations on hydrates are very important for the knowledge of transition properties between dilute aqueous solutions and molten electrolytes.

As a matter of fact, these electrolyte- water systems became gradually the object of intense attention and their study is now seriously expanding as much for technical applications as for theoretical reasons. Hydrates are used, or planned to be, in technologies such as ore leaching and extraction processes, waste-water treatment, chemical and electrochemical manufacturing, absorption-type refrigeration machines. Due to concern about pollution and security problems, areas of technological interest include energy storage and generation. For example, solar energy storage, exploitation of geothermal energy sources, molten salts based fluids in nuclear reactors which could contain more or less water, deliberately introduced or not. The knowledge of thermodynamic and transport properties, for example water vapor pressure, heat of vaporization, viscosity, electrical conductance..., as well as the influence of water concentration, temperature... on these properties, over the ranges of anticipated operating conditions, are essential in the design and operation of technical systems in which they are utilized.

With regard to scientific interest, the suggestion was made, now and then,1-8 that more progress in the understanding of very concentrated aqueous solutions could come from the consideration of solutions obtained by adding water to fused electrolytes rather than concentrating dilute aqueous solutions. Reciprocally, one would expect the structure of solutions where water plays the role of the solute, its mole fraction being less than about 0.5, be akin to that of the anhydrous molten electrolytes so that in the limit of vanishing water mole fraction the properties of the solutions would tend to those of the anhydrous electrolytes. From this point of view, any theoretical bringing-in regarding those solutions could contribute to more progress concerning the anhydrous electrolytes themselves.

Recently, electrolyte-water systems were investigated in the liquid phase over practically the whole water concentration range. Since these systems bridge the gap between anhydrous electrolytes and dilute aqueous solutions, they are designated by the expression "bridging electrolytewater systems", the electrolyte being a single one or a mixture of several components. Bridging systems lie at the heart of the present chapter. Electrolyte-water systems which do not cover the entire concentration range will also be examined or taken into account inasmuch as they cover a sufficiently large water mole fraction region, starting especially near the anhydrous electrolyte, so that they can give information on the transition of properties between those at the two extremes of the concentration scale.