Question

Nitric acid is an oxidising agent and reacts with $PbO$ but it does not react with $Pb{O}_2$. Explain why?

Answer 1

Reaction of $HN{O}_3$ with $PbO$
$PbO$ is a basic oxide and simple acid-base reaction takes place between $HN{O}_3$ (acid) and $PbO$ (base).

$2PbO+4HN{O}_3\to 2Pb(N{O}_3{)}_2+2H_{2}O$

Reactions of $HN{O}_3$ with $Pb{O}_2$
In $Pb{O}_2$, oxidation state of $Pb$ is $+4$ which is highest oxidation state of $Pb$.

Since $Pb$ is in its highest oxidation state, it cannot get oxidised further.

Thus, when $HN{O}_3$ reacts with $Pb{O}_2$, no reaction takes place since $Pb$ in $Pb{O}_2$ cannot be further oxidised by $HN{O}_3$.

Thus, $HN{O}_3$ reacts with $PbO$ and gives acid base reaction while $HN{O}_3$ does not reacts with $Pb{O}_2$