Mechanism of the permanganate—nitrite reaction. II. The role of complex formation in the kinetics of the reaction

✍ Scribed by L. Dózsa; I. Szilassy; M.T. Beck

• Publisher: Elsevier Science
• Year: 1977
• Tongue: English
• Weight: 534 KB
• Volume: 23
• Category: Article
• ISSN: 0020-1693
• DOI: 10.1016/s0020-1693(00)94737-6

✦ Synopsis

The kinetics of the reaction between permanganate and nitrite in acid medium were studied spectrophotometrically by the stopped flow method. The observed rate equation was v = k,[HN02] + kzk3 [HNOJ' [Mn( VII)] k3 [Mn(VII)] + k_zK [H+J [HNOa]

In perchloric acid medium at 25 + 0.1 "C, with an ionic strength of 0.1, the values of the rate constants were k, = 2 X 10M3 s-', kz = 10 mot-' dm3 s-', k3 = 5.3 X 10' rnor' dm3 s-l and kz = 50 moT' dm3 s-l.

According to the suggested mechanism, a complex is formed between Mn(VII) and nitrite, which is inert as regards the redox reaction, its stability constant being K = 3.5 X 10' moT' dm3. During the reaction the accumulation of Mn(IV) as an intermediate was observed. The rate is greatly decreased in the presence of the Hg(II) ion owing to the formation of Hg(II)-nitro complexes. Kinetic measurements showed that the stability constant of HgNOG is -IO4 moT' dm3.