(A) Oxidation state of Pb in Pb3O4⇒3x+(−8)=0
Pb3 must cancel out the −8 and therefore, Pb must have overall oxidation number of +8 or +8/3. However, oxidation numbers cannot be a fraction.
Pb3O4 actually exists as a mixture of PbO and PbO2 in the ratio 2:1. The oxidation states of each are +2 and +4. It can act as both acid and base. Hence, it is amphoteric in nature.
(B) Oxidation state of Sn in SnO2⇒x+(−4)=0⇒x=+4
SnO2 can act as acid and base therefore is amphoteric in nature.
(C) Oxidation state of Pb in PbO2⇒x+(−4)=0⇒x=+4 It is a base in nature.
(D) Oxidation state of C in CO2⇒x+(−4)=0⇒x=+4
It is acidic in nature.
(E) Oxidation state of Ge in GeO⇒x+(−2)=0⇒x=+2. It is amphoteric in nature.