Year of Award

2014

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Chemistry

Department or School/College

Department of Chemistry and Biochemistry

Committee Chair

Garon C. Smith

Commitee Members

J. B. Alexander (Sandy) Ross, Edward Rosenberg, Richard J. Field, Nancy Hinman

Keywords

3-D modelling, Acid-Base, Aqueous equilibrium, Metal Complexation, Redox, Solubiltiy

Abstract

This dissertation establishes a comprehensive approach to looking at aqueous equilibria phenomena over essentially all feasible compositions of two component solutions - acid-base titrations, metal-ligand complexation, oxidation-reduction couples and solubility of binary ionic compounds. Fundamental to this method is the definition of a composition grid above which numerous system properties can be plotted as three-dimensional trend surfaces to visualize important aspects of system behavior. These have been named "topos" because their appearance is similar to topographic maps. In each case Microsoft ExcelTM worksheets have been designed with embedded Visual BasicTM macros that provide an easy means for anyone to generate surfaces of interest. The only inputs required are thermodynamic values such as acid dissociation constants (Ka), overall formation constants (βs), standard reduction potentials (Eo) or solubility product constants (Ksp). Once the macro is started, the software generates equilibrium values for system parameters at every composition grid point and then constructs 3-D surfaces in plotting windows. The resultant plots can be rotated in any direction to enhance viewing of surface features. Several new chemical phenomena have been identified in the course of this project: 1) in acid-base systems buffering against dilution effects has been characterized more thoroughly than previously found in the literature. 2) New equations relating buffer capacity to titration procedures have been derived and visualized as topos. 3) Anti-buffering, a new behavior in metal-ligand complexation systems has been identified; it was confirmed experimentally with a Cu2+-ethylenediamine system where the activity of free Cu2+ ion increased more than 100-fold as the system was diluted more than 1300 times. 4) Overall trends in cell potentials have been clarified and utilized in describing why batteries supply a nearly constant voltage until suddenly dying. 5) A composition grid has been designed for future studies on the solubility of ionic compounds. The interactive Excel spreadsheets are easily adapted to use in pedagogic settings. Suggested PowerPoint teaching resources and explanations of the numerical methods used to solve the equilibrium calculations have been supplied as examples in the acid-base studies.

Download

Share

COinS
 

© Copyright 2014 Mohammad Mainul Hossain