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

Kinetics and mechanism of the redox reaction of hexakis(hydroxylamine)cobalt(III) ions with cerium(IV) ions

A. Olexová and Ľ. Treindl

Department of Physical Chemistry, Faculty of Natural Sciences, Komenský University, 816 50 Bratislava

Abstract: The kinetics and mechanism of the redox reaction of the Co(NH₂OH)₆³⁺ ions with Ce(IV) ions in H₂SO₄ soln. were studied polarog. The reaction order with respect to either reactant was detd. and the rate equation v = k[Ce(IV)][Co(NH₂OH)₆³⁺]^0.6 was derived. On the basis of the dependence of the exptl. rate const. on concn. of the H₃O⁺ ions and of HSO₄^- ions, it was concluded that the reactive Ce(IV) species is Ce(SO₄)₂. The activation parameters, i.e. enthalpy, ΔH*, and entropy, ΔS*, were evaluated from the temp. dependence of the rate const. as 64.6 kJ/mol and -24 J/mol.K, resp. The probable reaction mechanism is proposed. According to this mechanism, the reaction proceeds via the binuclear complex [(NH₂OH)₅Co-NH₂OH-Ce(SO₄)₂]³⁺ the decay of which is the slowest and rate-detg. step.

Full paper in Portable Document Format: 355a605.pdf

Chemical Papers 35 (5) 605–611 (1981)