Permanganate ion reacts with bromide ion in basic medium to give manganese dioxide and bromate ion. Write the balanced equation for the reaction using oxidation number method.
Skeletal equation is
`MnO_4^(-) +Br^(-) rarr MnO_2 +BrO_3^(-)`

Explanation

Step 1: Sketetal equation: `MnO_4^(-) + Br^(-) to MnO_2 + BrO_3^(-)`
Step 2: Permanganate ion is the oxidant and bromide ion is the redụctant.
`overset(+7)(Mn)overset(-2)(O_4^(-)) + overset(-1)(Br^(-)) to overset(+4)(Mn)overset(-2)(O_2) + overset(+5)(Br)overset(-2)(O_3^-)`
Step 3: Multiplying `MnaO_2` on the left and the right by 2 to equalise numbers.
`overset(+7)(2Mn)overset(-2)(O_4^(-)) + overset(-1)(Br^-) to 2overset(+4)(Mn)overset(-2)(O_2)+ overset(+5)(Br)oveset(-2)(O_3^-)`
Step 4: As the reaction is taking place in basic medium and the ionic charges are not equal on both sides, two OH-ions are added on the right to make ionic charges equal.
`2MnO_4^(-) +Br^(-) to 2MnO_2 + BrO_3^(-) +2OH^(-)`
Step 5: One molecule of `H_2O` is added on the left side to obtain the balanced redox equation.
`2MnO_4 +Br^(-) +H_2O - 2MnO_2 +BrO_3^(-) +2OH^(-)`