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Kinetics and mechanism of the oxidation of iron(II) ion by chlorine dioxide in aqueous solution
Author(s) -
Moore Evan R.,
Bourne Andrew E.,
Hoppe Todd J.,
Abode Philip J.,
Boone Steven R.,
Purser Gordon H.
Publication year - 2004
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.20023
Subject(s) - chemistry , chlorite , chlorine dioxide , aqueous solution , ionic strength , chlorine , inorganic chemistry , chloride , ion , ionic bonding , reaction rate constant , stoichiometry , reaction mechanism , reaction rate , kinetics , catalysis , organic chemistry , paleontology , quartz , physics , quantum mechanics , biology
The mechanism by which an excess of iron(II) ion reacts with aqueous chlorine dioxide to produce iron(III) ion and chloride ion has been determined. The reaction proceeds via the formation of chlorite ion, which in turn reacts with additional iron(II) to produce the observed products. The first step of the process, the reduction of chlorine dioxide to chlorite ion, is fast compared to the subsequent reduction of chlorite by iron(II). The overall stoichiometry isThe rate is independent of pH over the range from 3.5 to 7.5, but the reaction is assisted by the presence of acetate ion. Thus the rate law is given byAt an ionic strength of 2.0 M and at 25°C, k u = (3.9 ± 0.1) × 10 3 L mol −1 s −1 and k c = (6 ± 1) × 10 4 L mol −1 s −1 . The formation constant for the acetatoiron(II) complex, K f , at an ionic strength of 2.0 M and 25°C was found to be (4.8 ± 0.8) × 10 −2 L mol −1 . The activation parameters for the reaction were determined and compared to those for iron(II) ion reacting directly with chlorite ion. At 0.1 M ionic strength, the activation parameters for the two reactions were found to be identical within experimental error. The values of Δ H ‡ and Δ S ‡ are 64 ± 3 kJ mol −1 and + 40 ± 10 J K −1 mol −1 respectively. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 554–565, 2004