Development of Iterative Methods for the Exact Determination of Acid Dissociation Constants and Specific Reaction Rates in Various Ionic or Electrochemical Systems. A Review

Abstract

Theory and iterative methods for analysis of potentiometric titration data are presented in this paper. The methods concern titrations of (i) weak monoprotic acids, (ii) mixtures of weak acids with their conjugate bases (buffer solutions), (iii) mixtures of two monoprotic acids, (iv) solutions of polyprotic (di- and triprotic) acids with overlapping ionisation steps, and (v) mixtures of two diprotic acids. Using equations derived without approximations and data exclusively resulting from the buffer region of a titration curve, it is possible to extract the accurate values of the concentration(s) and thermodynamic dissociation constant(s) of the titrated acid(s), even when the titration is stopped well before the end-point of the titration. The main principles of the iterative methods can also be applied to the evaluation of chronoamperometric curves for various electrochemical mechanisms (ECECE, ECE, irreversible, quasi-reversible, and CE). Thus, it is possible to extract the kinetic parameters k1 and k2 of an ECECE mechanism using exclusively chronoamperometric data. The analysis of the chronoamperometric curves for the other mechanisms (ECE, irreversible, quasi-reversible, and CE) permits the extraction of the corresponding kinetic parameters even when the values of the diffusion coefficient D and the effective area A of the electrode are not known. A review with 52 references.