Rate of the Bromous Acid-Bromide Reaction Measured in a Br2-HOBr Buffer System in Sulfuric Acid Solution

Abstract

In the Belousov-Zhabotinsky system bromine species of oxidation states - 1 to 5 are important for the start and for the inhibition of the autocatalytic reaction steps. Especially, the reaction of Br- with HBrO2 competes with the oxidation of Ce3+ by BrO2 formed from HBrO2 and HBrO3. In our investigation the reaction of Br- with HBrO2 (solvent 1 M sulfuric acid) is followed spectroscopically in a mixture of bromine and hypobromous acid, which system works as a buffer for bromide. Including experiments on the hydrolysis of Br2 and on the solubility product of AgBr in 1 M sulfuric acid solution direct information about the rate constant kl of the Br-/HBrO2 reaction is obtained (k1 = 2.5 × 106 M-2 s-1 at 20 °C and 4× 106 M-2 s-1 at 25°C, which values are valid in the range of 0.01 to 1 M sulfuric acid).