The difference in the reactivity of the metal oxides is because of he oxidation staes of the metal
`overset(+2)2Pbo+4HCIrarroverset(+2)2PCI_(2)+2H_(2)O`
`overset(+4)2PbO_(2)+4HCIrarroverset(+2)2PbCI_(2)+CI_(2)+2H_(2)O`
atom in the two oxides.In the first reaction, oxidtion state of Pb does not change but it undergoes a change in the second case.Therefore `PbO_(2)` reacts at faster rate than Pbo.