In the given reaction, the oxidation number of bromine increases from 0 to +1 and decreases from 0 to -1 . Due to this reason bromine is both oxidised as well as reduced. :H2O+Br20⟶HOBr+HBr−1 Caution Some students understood that the given reaction is redox reaction, but confuse with fact that redox reaction is the reaction in both oxidation and reduction occurs.