Why the Acidity of Bromic Acid Really Matters for Kinetic Models of Belousov-Zhabotinsky Oscillating Chemical Reactions

Glaser, Rainer

doi:10.4172/2157-7544.1000e115

Cited by 2 publications

(6 citation statements)

References 33 publications

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“…The manganese-catalyzed B−Z reaction is inherently connected to the chemistry of bromine. 20 The reaction consists of two main parts: the positive feedback process is that bromate oxidizes Mn(II) ions to produce autocatalytic bromic acid and bromine dioxide under acidic conditions and the negative feedback process is that Mn(III) ions react with bromomalonic acid to release Br − ions. Then, Br − ions react with bromic acid rapidly, which is an autocatalytic intermediate.…”

Section: Resultsmentioning

confidence: 99%

Effects of Selenium Species on the Belousov–Zhabotinsky Reaction

Luo

et al. 2019

J. Phys. Chem. A

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The effects of selenium species on the Belousov–Zhabotinsky (B–Z) reaction were investigated by adding them to the system before and during oscillation. When selenium species were added into the system before oscillation, sodium selenite prolonged the induction period, whose effect was strong as sodium selenite could consume malonic acid to prohibit the accumulation of bromomalonic acid. For selenomethionine and selenocystine, their effects were derived from their reaction with •CH2COOH and •Br2 – producing a radical cation of selenoamino acids, which prohibited the accumulation of bromomalonic acid. Here, the selenium atoms in selenoamino acids, as reactive centers, took part in the redox reaction. As a result, the induction period was prolonged. However, as a diselenide, selenocystine can reduce bromate in acidic medium, which led to shortening of the induction period. Therefore, the effect of selenocystine on the induction period was the result of two opposite effects. Nanoselenium shortened the induction period in a certain concentration range because bromate was directly reduced by nanoselenium and the accumulation of bromomalonic acid was promoted. Furthermore, the dose perturbation effect was investigated by the injection of nanoselenium during oscillation. It was found that the amplitude was increased or decreased in a dose-dependent fashion when nanoselenium was injected at peak or trough of the time-dependent redox potential curve.

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Section: Resultsmentioning

confidence: 99%

Effects of Selenium Species on the Belousov–Zhabotinsky Reaction

Luo

et al. 2019

J. Phys. Chem. A

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“…Experimental pK a (HBrO 3 ) values of 1.87, 47 0.7, 48 and −0.29 49 were reported, and most recently, Cortes and Faria concluded that pK a (HBrO 3 ) < −0.5. 50 It is important 24,25 to firmly establish pK a (HBrO 3 ) because this value affects the kinetics of the BZR reaction. Mixtures of sulfuric acid (H 2 A = H 2 SO 4 ) and bromate salts (B − = BrO 3…”

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confidence: 99%

“…16,17 From an educational perspective, analyses of multiequilibria present excellent opportunities for the synergetic integration of science and math education, 18,19 and such activities are very much in the spirit of the Next Generation Science Standards 20,21 and its implications for college teaching. 22,23 Stimulated by our interest in understanding aqueous solutions of sulfuric acid and bromate in the context of studies of Belousov−Zhabotinsky oscillating reactions, 24,25 we consider here the general case of the coupled equilibria given by the dissociation and equilibrium equations (2)…”

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confidence: 99%

“…28−33 The desire to understand the precise mechanisms of oscillating chemical reactions provided strong incentives to study the chemistry of bromous acid. 24,25,36 The need to obtain accurate equilibrium concentrations for the H 2 SO 4 /BrO 3 − system motivated the work reported here, and we studied a typical H 2 SO 4 /BrO 3 − mixture as a function of the K a (HBrO 3 ) value.…”

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confidence: 99%

“…Stimulated by our interest in understanding aqueous solutions of sulfuric acid and bromate in the context of studies of Belousov–Zhabotinsky oscillating reactions, , we consider here the general case of the coupled equilibria given by the dissociation and equilibrium equations normalH 2 normalO ⇄ normalH + + OH − , goodbreak0em1em⁣ K normalw = [ H + ] [ OH − ] normalH 2 normalA ⇄ normalH + + HA − , goodbreak0em1em⁣ K 11 = [ H + ] [ HA − ] / [ H 2 A ] HA − ⇄ normalH + + normalA 2 − , goodbreak0em1em⁣ K 12 = [ H + ] <...…”

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Dynamical Approach to Multiequilibria Problems for Mixtures of Acids and Their Conjugated Bases

et al. 2014

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Mathematical methods are described for the determination of steady-state concentrations of all species in multiequilibria systems consisting of several acids and their conjugated bases in aqueous solutions. The main example consists of a mixture of a diprotic acid H 2 A, a monoprotic acid HB, and their conjugate bases. The reaction equations lead to a system of autonomous ordinary differential equations for the species concentrations. The traditional equilibrium approach is briefly reviewed. Single variable polynomials are determined that are satisfied by the equilibrium proton concentrations. The remaining species are then given explicitly by rational functions of these proton concentrations, the equilibrium constants, and the initial concentrations of the other species. A quintic polynomial was derived to determine the equilibrium proton concentration for the example system. It is shown to reduce to a quartic polynomial in the absence of the second acid HB. An alternative dynamical approach to the equilibrium problem is described that involves the formulation of the kinetic rate equations for each species, which together constitute a nonlinear system of ordinary differential equations. The equilibrium concentrations are determined by evolving the initial concentrations via this dynamical system to their steady state. This dynamical approach is particularly attractive because it can easily be extended to determine equilibrium concentrations for arbitrarily large multiequilibria systems. With the equations provided here and some knowledge of computing software, the fast and accurate computation of equilibrium concentrations becomes feasible for the education of upper-division undergraduate and graduate students as well as for the study of research problems. This dynamical method also serves to introduce students to nonlinear dynamical systems, which are essential for the study of dynamic problems in chemistry, for example, oscillatory reactions.

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Why the Acidity of Bromic Acid Really Matters for Kinetic Models of Belousov-Zhabotinsky Oscillating Chemical Reactions

Cited by 2 publications

References 33 publications

Effects of Selenium Species on the Belousov–Zhabotinsky Reaction

Effects of Selenium Species on the Belousov–Zhabotinsky Reaction

Dynamical Approach to Multiequilibria Problems for Mixtures of Acids and Their Conjugated Bases

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