ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Kinetic study of cerium(IV) complexes with oxalic acid

Ľ. Treindl

Department of Physical Chemistry, Faculty of Natural Sciences, Komenský University, Bratislava

Abstract: The paper refers to the results of kinetic study involving the oxidation of oxalic acid by cerium(IV) sulfate in sulfuric acid. It has been ascertained that the reaction in this solution is governed by kinetic equation of second order k t = x/a(a — x). Using the Eyring equation kinetic thermodynamic parameters ΔH^≠ = 24.12 kcal/mol and ΔS^≠ = = 26.4 cal/deg mol were determined. The velocity constant of the studied reaction decreases with the increasing concentration of oxalic acid. The decrease of velocity constant with increasing concentration of oxalic acid can be rationalized by stepwise formation of cerium(IV) oxalate complexes, the reactivity of which decreases with the increasing amount of oxalate ions linked by coordination bonds. The formulas making it possible to determine the composition of these complexes and their consecutive complexity constants were derived. It has been shown by the graphic analysis that the increasing concentration of oxalic acid results in formation of relatively inactive complex Ce(S0₄)₂(C₂0₄)₂^4- of consecutive complexity constant k = 1816 to the detriment of the intermediate complex Ce(S0₄)₂(C₂0₄)^2-. The probable reaction mechanism is discussed on the basis of kinetic data obtained polarographically.

Full paper in Portable Document Format: 226a407.pdf (in Slovak)

Chemical Papers 22 (6) 407–414 (1968)