Q.Explain the bleaching action of ozone and state how it differs mechanistically from the bleaching action of chlorine.

[!TLDR] Ozone bleaches by releasing oxidising nascent oxygen that destroys the coloured pigment irreversibly, unlike chlorine's bleaching, which works via HOCl formed in water. [!ANSWER] Ozone bleaches oxidatively via nascent oxygen ($\text{O}_3 \rightarrow \text{O}_2 + [\text{O}]$), a d …

Ozone's bleaching action arises from its tendency to decompose, releasing highly reactive nascent (atomic) oxygen: $\text{O}_3 \rightarrow \text{O}_2 + [\text{O}]$ This nascent oxygen oxidises and thereby destroys the chemical structure of coloured organic pigments, converting them into colourless products -- an essentially permanent, oxidative bleaching process. Chlorine's bleaching action proceeds by a different route: chlorine first reacts with moisture in the material being bleached to form hypochlorous acid, $\text{Cl}_2 + \text{H}_2\text{O} \rightarrow \text{HCl} + \text{HOCl}$, and it is this HOCl that supplies the oxidising nascent oxygen ($\text{HOCl} \rightarrow \text{HCl} + [\text{O}]$) that actually destroys the colour -- so chlorine's bleaching, unlike ozone's, requires moisture to be present and proceeds through an intermediate acid rather than decomposing directly. Both mechanisms are oxidative and, once the coloured pigment's structure is chemically broke …

Write ozone's direct decomposition to nascent oxygen, then contrast it with chlorine's route via HOCl formed from atmospheric/ …

Describing ozone's bleaching as identical in mechanism to chlorine's; confusing oxidative bleaching (permanent, by O3/Cl2) …