Q.Balance the following equations by the ion-electron method.

Both standard methods for balancing a redox equation rest on the same principle: the total electrons donated by the reducing agent must equal the total electrons gained by the oxidising agent.

Oxidation number method (5 steps):

1. Identify, via oxidation numbers, which atom is oxidised and which is reduced, and by how many electrons each.
2. Equalise electrons lost and gained by multiplying each species by suitable integers (matching how many atoms of that element appear per formula unit on each side).
3. Balance the oxidised/reduced species on the product side to match.
4. Balance every other element except H and O.
5. Balance H and O last (O should then balance automatically if everything else is correct).

Ion-electron (half-reaction) method, used for ionic redox reactions:

1. Identify the oxidised and reduced species via oxidation numbers.
2. Write two separate half-equations: one for oxidation, one for reduction.
3. Balance the atoms and charge in each half-equation separately (add H₂O to balance O, then H⁺ to balance H, in acid medium).
4. Multiply each half-equation by whatever integer makes the electrons lost equal the electrons gained, then add the two half-equations together (the electrons cancel). …