The stoichiometry of the reaction between chlorite and iodine in the pH range 2–5 and at low [I−] has been determined to be 5C102− + 2I2 + 2H2O − 5C1− + 4IO3− + 4H+. The kinetics of this reaction have been studied by stopped-flow spectrophotometry at 22.2 °C and variable ionic strength (10−2−10−1 M). The rate law is −½d[I2]/dt = (k1/[ClO2−] +/k2[C1O2−]/[H+] + k3)[I2], where k1 = (1.1 ± 0.4) × 10 M−1 s−1, k2 = (1.1 ± 0.1) × 10−2 s−1, and k3 = (5.4 ± 0.3) × 10−1 s−1. A mechanism is proposed involving formation of the key intermediate IC1O2 by reactions between chlorite and I2, I2OH−, and IOH2+. The rate constant for the elementary reaction C1O2− + I2 → IC1O2 + I− is given by k1. The value of the rate constant for the elementary reaction I2OH− + ClO2− - IClO2 + I− + OH− is 7.7 × 107 M−1 s−1. We have identified k3 with the reaction I2 + H2O → IOH2+ + I−.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry