Kinetics and Mechanism of the Decomposition of Chlorous Acid

A. Horváth, I. Nagypál, G. Peintler, Irving R. Epstein, Kenneth Kustin

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

The kinetics of decomposition of aqueous chlorous acid has been reinvestigated at pH 0.7-1.9, ionic strength 1.0 M (HSO4 -/SO42-), and temperature 25.0 ± 0.1 °C. Optical absorbances were collected in the 240-450 nm wavelength range for up to ∼90% decomposition for time series lasting as long as 2 days. The number of absorbing species was investigated by matrix rank analysis; no absorbing intermediate was formed in significant concentration during the decomposition. Of the many mechanistic models tested, the one that fit best included the following reactive intermediates: HOCl, Cl2O 2, Cl2O3, .ClO, .OH. The stoichiometric ratio of ClO2 produced to Cl(III) consumed varies with pH and [Cl-]. Reaction of Cl2O3 with Cl(III) yields chlorate exclusively. Reaction of Cl2O3 with Cl- favors ClO2 over chlorate, but does not entirely exclude chlorate, because it is produced by hydrolysis of Cl2O 2. Invoking Cl2O3 explains the variation in stoichiometric ratio as well as the maximum observed in the initial rate of ClO2 formation as a function of pH. The kinetics of chlorous acid decomposition cannot be quantitatively fit through the last stages of the reaction without postulating a first-order decomposition. Scission of chlorous acid to give short-lived hydroxyl and chlorine-(II) monoxide is a plausible route for this process. A set of best-fit and literature-derived parameters is presented for the complete mechanism.

Original languageEnglish
Pages (from-to)6966-6973
Number of pages8
JournalJournal of Physical Chemistry A
Volume107
Issue number36
DOIs
Publication statusPublished - Sep 11 2003

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Chlorates
chlorates
Decomposition
decomposition
acids
Kinetics
kinetics
Chlorine
Ionic strength
Hydroxyl Radical
chlorine
hydrolysis
Time series
cleavage
Hydrolysis
routes
chlorous acid
Wavelength
matrices
wavelengths

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Kinetics and Mechanism of the Decomposition of Chlorous Acid. / Horváth, A.; Nagypál, I.; Peintler, G.; Epstein, Irving R.; Kustin, Kenneth.

In: Journal of Physical Chemistry A, Vol. 107, No. 36, 11.09.2003, p. 6966-6973.

Research output: Contribution to journalArticle

Horváth, A. ; Nagypál, I. ; Peintler, G. ; Epstein, Irving R. ; Kustin, Kenneth. / Kinetics and Mechanism of the Decomposition of Chlorous Acid. In: Journal of Physical Chemistry A. 2003 ; Vol. 107, No. 36. pp. 6966-6973.
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