In the following reaction: 3Br2 + 6CO32- + 3H2O = 5Br - + BrO3- + 6HCO3-

In the oxidation process the oxidation number of bromine changes from 0 (in Br₂) to +5 (in BrO₃^–) and in reduction, oxidation number of bromine changes from 0 (in Br₂) to -1 (in Br ^–).