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The Investigation of Equilibria in Solution

M. Maeder^a and H. Abdollahi^b,*

^aDepartment of Chemistry, University of Newcastle, Australia
^bInstitute of Advanced Studies in Basic Sciences, Zanjan, Iran

This contribution describes the practical and computational aspects relevant for the quantitative analysis of chemical equilibria. First a systematic nomenclature based on stability constants is introduced. Next, practical aspects of potentiometric pH titrations and spectrophotometric titrations are discussed. The description of the computational aspects includes the Newton-Raphson algorithm that allows the computation of all species concentrations for a given model, set of formation constants and total component concentrations. The second computational part introduces the Newton-Gauss algorithm for non-linear data fitting. Three practical examples illustrate all the above. They include the spectrophotometric investigations of the interaction of Bi(III) with Cl^-, of Cu(II) with EDTA and the potentiometric investigation of the Zn(II) ethylenediamine system. All Matlab softwares for the data generation and analysis are available from the authors.

Keywords: Chemical equilibrium, Titration, Non-linear least-squares fitting, Protonation equilibria, Complexation equilibria