Kinetics and mechanism of the reaction between chlorine(III) and bromide ion

Journal Article · Thu Dec 04 04:00:00 EST 1986 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100283a023· OSTI ID:6953196

Valdes-Aguilera, O; Boyd, D W; Epstein, I R; Kustin, K

The stoichiometry and kinetics of the reaction between chlorine(III) and bromide ion were studied spectrophotometrically at 25.0 +/- 0.5 /sup 0/C and ionic strength 1.2 M (NaClO/sub 4/). The main products are Br/sub 3//sup -/ and Cl/sup -/ when bromide ion is in excess, ClO/sub 2/ and Br/sub 2/ when chlorine(III) is in excess. With sufficient acid and excess bromide ion, the stoichiometry of the reaction is HClO/sub 2/ + 6Br/sup -/ + 3H/sup +/ ..-->.. 2Br/sub 3//sup -/ + Cl/sup -/ + 2H/sub 2/O. The rate law for this reaction is (1/2)d(Br/sub 3//sup -/)/dt= k(H/sup +/)(Br/sup -/)(Cl(III)) where k = 9.51 +/- 0.14) x 10/sup -2/ M/sup -2/ s/sup -1/. When the reaction is carried out with (Cl(III)) > (Br/sup -/), the stoichiometry is difficult to define. In the range (Cl(III)) approx. = (1.50 - 2.00) x 10/sup -3/ M, (Br/sup -/) approx. = 5.00 x 10/sup -4/ M, and (perchloric acid) approx. = 0.20 M, a clock reaction occurs, the lag time of which decreases with addition of small amounts (<10/sup -4/ M) of molecular bromine. The complex rate law for the chlorine(III)-bromide ion reaction with excess Cl(III) can be explained by a 16-step mechanism including oxidation of bromide ion to bromine by chlorine(III), reduction of bromine to bromide ion, and decomposition of chlorous acid. A reduced set of 10 reactions and associated rate and equilibrium constants successfully modeled the clock reaction by computer simulation.

• Research Organization: Brandeis Univ., Waltham, MA
• OSTI ID: 6953196
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 90:25; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
ANIONS
BROMINE
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORINE
DATA
ELEMENTS
EXPERIMENTAL DATA
HALOGENS
INFORMATION
IONS
KINETICS
MEDIUM TEMPERATURE
NONMETALS
NUMERICAL DATA
REACTION KINETICS
SPECTROPHOTOMETRY
STOICHIOMETRY