Kinetics and mechanism of the oxidation of sulfite by chlorine dioxide in a slightly acidic medium |
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Authors: | Horvath Attila K Nagypal Istvan |
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Institution: | Department of Physical Chemistry, University of Szeged, Szeged, P.O. Box 105, H-6701, Hungary. |
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Abstract: | The sulfite-chlorine dioxide reaction was studied by stopped-flow method at I = 0.5 M and at 25.0 +/- 0.1 degrees C in a slightly acidic medium. The stoichiometry was found to be 2 SO(3)(2-) + 2.ClO(2) + H(2)O --> 2SO(4)(2) (-) + Cl(-) + ClO(3)(-) + 2H(+) in *ClO(2) excess and 6SO(3)(2-) + 2*ClO(2) --> S(2)O(6)(2-) + 4SO(4)(2-) + 2Cl(-) in total sulfite excess (S(IV)] = H(2)SO(3)] + HSO(3)(-)] + SO(3)(2-)]). A nine-step model with four fitted kinetic parameters is suggested in which the proposed adduct *SO(3)ClO(2)(2-) plays a significant role. The pH-dependence of the kinetic traces indicates that SO(3)(2-) reacts much faster with *ClO(2) than HSO(3)(-) does. |
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