Balance the ionic equation by half reaction method O3+ Br- -------> O2 + BrO-

Answer:-

Step -1  

       Find the oxidation number of Br in BrO-

       in combination state oxygen has oxidation number = - 2 

             Br + O = - 1 

               Br -2 = -1 

                   Br = +1  

Step -2 

        write oxidation half reaction 

               Br-  <-----------> BrO- 

               -1                       +1

       here oxidation number of Br is increasing by 2 

       so add 2 electron to balance it 

       we get 

              Br-  <-----------> BrO-   + 2e-             

Step -3 

add OH - ions to balance the charge reaction 

Br- +  2OH-   <----------->BrO-   + 2e

Step - 4 

add H2O to balance the hydrogen and oxygen 

Br- +  2OH-   <----------->BrO-   +H2O +  2e 

balanced oxidation half reaction

 Br- +  2OH-   <----------->BrO-   +H2O +  2e   ---------------(1)

similarly you can get balanced half reduction reaction 

Balanced reaction half reaction 

O3 + H2O + 2 e- <-----------> O2 + 2 OH-        ---------------(2)

add both equations we get 

Br- +  2OH-  + O3 + H2O + 2 e- <-----------> BrO-   + 2e + O2 + 2 OH-

simplify the equation we get

O3+  Br- <----------->O2 +  BrO-

Answer : -  Equation was already balanced 

Balance the ionic equation