How many of the following will give `O_2` on heating ?
`KMnO_4, K_2,Cr_2O_7, ZnO,Na_2O, PbO_2,Pb_3O_4,Pb(NO_3)_2 , NH_4NO_3`

Answer

5

Explanation

`KMnO_4 overset(Delta) rarr MnO_2 + K_2MnO_4 + O_2`
`K_2 Cr_2O_7 overset(Delta) rarr K_2CrO_4 + Cr_2 O_3 + O_2`
`ZnO overset(Delta) rarr O^(-2) rarr O_2 + 2e^(-)` (Crystal deffect )
`PbO_2 rarr PbO + O_2`
`Pb_(3)O_4 rarr PbO + O_2`
`Pb(NO_3)_2 rarr PbO + NO_2 + O_2`
`NH_4 NO_3 rarr N_2O + H_2O`