The unbalanced redox reaction is MnO4−+C,O42−+H+→Mn2++CO2+H2O (i) Balanced C atoms
+7
MnO4
+C2O42−+H+→Mn2++2CO2+H2O Oxidation state of Mn decreases from +7 to +2. To balance the increase or decrease in oxidation number, multiply Mn containing species with 2 and C containing species with 5. 2MnO4−+5C2O42−→2Mn2++10CO2 (ii) Balance ′O′ atoms by adding 8 water molecules to the product side. 2MnO4−+5C2O42−→2Mn2++10CO2+8H2O (iii) Balance 'H' atoms by adding 16H+ions to the reactant side. 2MnO4−+5C2O42−+16H+→2Mn2++10CO2+8H2O Hence, MnO4−⇒2C2O42−⇒5,H+=16