The correct option is
B 3H2O2+2MnO−4⟶3O2+2MnO2+2OH−+2H2OThe unbalanced redox equation is as follows:
H2O2+MnO−4⟶O2+MnO2(basic)
All atoms other than H and O are balanced.
The oxidation number of Mn changes from +7 to +4. The change in the oxidation number is 3.
The oxidation number of O changes from -1 to 0. The change in the oxidation number per O atom is 1. The total change in oxidation number for 2 O atoms is 2.
To balance the increase in the oxidation number with decrease in the oxidation number multiply MnO−4 and MnO2 with 2 and multiply H2O2 and O2 with 3..
3H2O2+2MnO−4⟶3O2+2MnO2(basic)
To balance O atoms, add four water molecules on RHS.
3H2O2+2MnO−4⟶3O2+2MnO2+4H2O(basic)
To balance H atoms, add 2H+ on LHS.
3H2O2+2MnO−4+2H+⟶3O2+2MnO2+4H2O(basic)
Since the reaction occurs in basic medium, add 2 OH− ions on either side.
3H2O2+2MnO−4+2H++2OH−⟶3O2+2MnO2+4H2O+2OH−(basic)
On LHS, 2 H+ ions combine with 2 OH− ions to form 2 water molecules which cancels with two water molecules on RHS.
3H2O2+2MnO−4⟶3O2+2MnO2+2OH−+2H2O
This is the balanced chemical equation.