Question

Balance the following reaction by ION-ELECTRON method 

Cl₂(g) + OH^– → Cl^–(aq) + ClO₃^–(aq) + H₂O (in basic medium)

Answer 1

Cl₂(g) + OH^– → Cl^–(aq) + CIO₃^–(aq) + H₂O

Oxidation half-reaction

Cl₂(g) + 6H₂O(l) → 2ClO₃^–(aq) (… Go for balancing oxygen is a abasic media odd off on RHS)

Cl₂(g) + 6H₂O(l) + 12OH^– → 2ClO₃^-(aq) + 12H₂O(l)

Cl₂(g) + 12OH^–(aq) → 2ClO₃^–(aq) + 6H₂O(l) (now balance e-)

Cl₂(g) + 12OH^–(aq) → 2ClO₃^–(aq) + 6H₂O(l) + 10e^– . ..(1)

Reduction half-reaction

Cl₂(g) → Cl^–(aq)

Cl₂(g) → 2Cl^–(aq)

Cl₂(g) + 3e → 2Cl^–(aq) …(2)

Multiply equation no. (2) by 5 to equalize electrons

Add both the half-reactions