Q.iv. What happens when a. Lead sulfide reacts with ozone (O$_3$). b. Nitric oxide reacts with ozone.

Ozone oxidises mercury to HgO, causing the classic 'tailing of mercury'.

Ozone is a powerful oxidising agent. It oxidises mercury to mercuric oxide:

2 Hg + 2 O3 -> 2 HgO + 2 O2 (i.e. Hg + O3 -> HgO + O2)

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NO catalytically depletes ozone: $NO+O_3\rightarrow NO_2+O_2$, then $NO_2+O\rightarrow NO+O_2$ (NO regenerated).

Nitric oxide (NO) reaching the stratosphere (from supersonic aircraft exhaust, or naturally from $N_2O$) catalytically destroys ozone in a chain cycle:

$NO + O_3 \longrightarrow NO_2 + O_2$

$NO_2 + O \longrightarrow NO + O_2$

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$O_3$ decomposes to release highly reactive nascent oxygen, making it a strong oxidising agent.

Ozone is thermodynamically unstable and readily decomposes: $O_3 \rightarrow O_2 + [O]$ (nascent/atomic oxygen). This nascent oxygen atom is extremely reactive and readily oxidises other substances, accepting electrons easily. Because one of the three oxygen atoms is very loosely bound and is easily given up as nascent oxygen, ozone acts as a powerful oxidising agent, e.g. it oxidises mo …