Question

In passing chlorine gas through a concentrated solution of alkali, we get chloride and chlorate ions. Obtain balanced chemical equation for this reaction by ion -electron method. Obtain balanced chemical equation for this reaction by ion -electron method.

Answer 1

Step 1: Write the skeletal equation for the given reaction.

Cl₂(g) + OH^-(aq) → Cl^-(aq) + ClO₃^-(aq) ...(i)

Step 2 : Write the ON of all the elements above their respective symbols 

O.N. of Cl increases by 5 per Cl atom

O.N. of Cl decreases by 1 per Cl atom Total increase = 2 x 5 = 10 Total decrease = 2 x -1 = -2

Step 3 : Find out the oxidant and the reductant and split the skeletal Eq (i) into two half reactions.

Step 4 : To balance the reduction half equation (ii). (a) Balance all atoms.

Cl₂(aq) →2Cl^–(aq) …(iv)

(b) Balance oxidation number by adding electrons.

Cl₂(g) + 2e^– →2Cl^–(aq) …(v)

represents the balanced reduction half reactions.

Step 5 : To balance the oxidation half equation (iii)

(a) Balance all atoms Cl₂(g) »2ClO₃^–

(b) Balance ON by adding electrons

Cl₂(g) → 2ClO₃^–(aq) + 10e^– … (vi)

(c) Balance charge by adding OH” ions

Cl₂(g) + 120H^–(aq) → 2ClO₃^–(aq) + 10e^– … (ix)

(d) Balance O atoms, the RHS of Eq. (viii) contains six O atoms but on the LHS there are 12. Therefore, add 5H₂O to the RHS, we have

This represents the final balanced redox equation.

Comments

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