Why do the following reactions proceed differently? `Pb_(3)O_(4)+8HClrarr3PbCl_(2)+Cl_(2)+4H_(2)O` and `Pb_(3)O_(3)+4HNO_(3)rarr 2Pb(NO_(3))_(2)+PbO_(2)+2H_(2)O`

Explanation

`Pb_(3)O_(4)` is actually a mixed oxide of PbO and `PbO_(2)`. In `PbO_(2)`, lead is present in `+4` oxidation state and in PbO it is `+2. PbO_(2)` thus can act as an oxidant (oxidising agent) and, therefore, can oxidise `Cl^(-)` ion of `HCl` into chlorine. PbO is a basic oxide. The reaction is
`Pb_(3)O_(4)+8HClrarr 3PbCl_(2)+Cl_(2)+4H_(2)O`
can be splitted into two reactions namely:
`2PbO+4HClrarr 2PbCl_(2)+2H_(2)O` (acid - base reaction)
`overset(+4)(PbO_(2))+overset(-1)(4HCl)rarroverset(+2)(PbCl_(2))+underset("(redox reaction)")(overset(0)(Cl_(2))+2H_(2)O)`
`HNO_(3)` being strong oxidising agent, the reaction between `PbO and HNO_(3)` do not take place. The acid-3 base reaction can be possible between P`hO and HNO_(3)` as follows: `2PbO+4HNO_(3)rarr 2Pb(NO_(3))_(2)+2H_(2)O`