(i) Chlorine bleaching action is due to oxidation while that of sulphur dioxide is due to reduction. Hence, the substance bleached by SO 2 is reoxidised by the oxygen of the air to its original state.

Cl 2 bleaches coloured material by oxidation and thus bleaching is permanent.

Cl 2 + H 2 O ⎯→ 2HCl + [O]

Coloured material + [O] ⎯→ Colourless

On the other hand beaching by SO 2 is by reduction and thus temporary because colourless articles are further oxidised by air.

SO 2 + 2H 2 O ⎯→ 2H 2 SO 4 + 2[H]

Coloured material + [H] ⎯→ Colourless coloured

(ii) Ι 2 is a covalent molecule. Thus, its solubility is less in polar solvent, i.e., water. Potassium iodide combines with iodine and forms a polyhalide which is an ionic compound. Being ionic, K Ι 3 is more soluble.

K Ι + Ι 2 K Ι 3 (K + Ι 3 – ) brown solution