Question

An aqueous solution of SO2 acts as a reducing agent to reduce aqueous KMnO4 to MnSO4(s). Write a balanced
chemical equation for this reaction.

Answer 1

The balanced equation :

5SO2 (aq) + 2KMnO4(aq) + 2H2O ------> 2MnSO4(aq) + K2SO4(aq) + 2H2SO4(aq)

How we can arrive above equation:

Reduction reaction: Mn(7+) is reduced to Mn(2+) i.e. Mn(7+) + 5e- -----> Mn(2+)

Oxidation reaction: S(+4) is oxidized to S(+6) i.e. S(+4) -----> S(+6) + 2e-

Now we can balance this on the basis of number of electrons. Multiply reduction reaction equation by by 2 and oxidation reaction equation by 5.

So

2 Mn(7+) + 10e- -----> 2 Mn(2+)

5 S(+4) -----> 5 S(+6) + 10 e-

Use the same coefficients in the combined reaction along with H2O to balance hydrogen and oxygens.