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Some General Features in the Autocatalytic Reaction between Sulfite Ion and Different Oxidants
Author(s) -
Molnár István,
Takács Nándor,
KurinCsörgei Krisztina,
Orbán Miklós,
Szalai István
Publication year - 2013
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.20782
Subject(s) - chemistry , autocatalysis , protonation , sulfite , oxidizing agent , reaction rate constant , autocatalytic reaction , inorganic chemistry , equilibrium constant , titration , titration curve , proton , ion , kinetics , catalysis , organic chemistry , statistical physics , physics , quantum mechanics
ABSTRACT The autocatalytic oxidation of a weak acid is a common building block of the pH oscillators. These reactions can be described by a simple general scheme that includes a protonation equilibrium and the oxidation of the protonated form of the weak acid. Here we show that independently from the chemical nature of the oxidizing agent, these reactions bear some general features, namely (1) the change in pH (ΔpH) observed during the reaction is determined by the acidity constant ( K HA ) and by the initial concentration of the unprotonated form of the weak acid (A − ): Δ pH = − ( pK HA + log [ A − ] i ) , (2) the inflection time of the autocatalytic reaction ( t i ) depends reciprocally on K HA and on the initial hydrogen ion concentration, and (3) in the presence of a competitive reversible proton‐binding component ( D − ), that is not involved in the oxidation process, ΔpH follows a titration‐like curve as the concentration of D − is increased, t i is only slightly affected but the maximum rate of the autocatalytic process is significantly reduced. The slowing of the overall reaction is proportional to the acidity constant of the proton‐binding component.