The correct option is C 2,5
H2O2(aq)+Cl2O7(aq)→ClO−2(aq)+O2(g)
Oxidation state of O in H2O2=−1
Oxidation state of O in O2=0
Oxidation state of Cl in Cl2O7=+7
Oxidation state of Cl in ClO−2=+3
Clearly, H2O2 is undergoing oxidation and Cl2O7 is undergoing reduction.
using the formula of n-factor given above,
nf of H2O2=2
nf of Cl2O7=8
simplest ratio of nf of H2O2:Cl2O7 is 1:4
Cross multiplying these with nf of each other.
we get,
4H2O2(aq)+Cl2O7(aq)→ClO−2(aq)+O2(g)
Balancing the main elements on both sides, generally oxygen is not balanced in this step but we will balance as it is undergoing oxidation in this reaction.
4H2O2(aq)+Cl2O7(aq)→2ClO−2(aq)+4O2(g)
Adding the H2O to balance the oxygen,
4H2O2(aq)+Cl2O7(aq)→2ClO−2(aq)+4O2(g)+3H2O
Adding H+ to balance hydrogen,
4H2O2(aq)+Cl2O7(aq)→2ClO−2(aq)+4O2(g)+3H2O+2H+
Now adding OH− to both sides to combine with H+ and make it H2O,
4H2O2(aq)+Cl2O7(aq)+2OH−→2ClO−2(aq)+4O2(g)+3H2O+2H++2OH−
4H2O2(aq)+Cl2O7(aq)+2OH−→2ClO−2(aq)+4O2(g)+5H2O
This is the final balanced equation.
We can also see that charge on both sides is -2. which also indicates that the equation is balanced now.
4H2O2(aq)+Cl2O7(aq)+2OH−→2ClO−2(aq)+4O2(g)+5H2O
So, 2, 5 moles of OH− and H2O respectively are present in balanced equation.