Question

Pb3O4+ 8 HCL GIV 3 PBCL2 +CL2+4H2O

PB3O4+4HNO3 GIV 2PB(NO3)2+PBO2+2H2O

WHICH OF THE PROCEED DIFFERENTLY.

Answer 1

It is the nature of PbO₂ against HNO₃ that makes the reaction different from the one that follows with HCl.

• Pb₃O₄ is actually a stoichiometric mixture of 2 mol of PbO and 1 mol of PbO₂. In PbO₂, lead is present in +4 oxidation state, whereas the stable oxidation state of lead in PbO is +2.
• PbO₂ thus can act as an oxidant (oxidising agent) and, therefore, can oxidise Cl ^– ion of HCl into chlorine. We may also keep in mind that PbO is a basic oxide. Therefore, the reaction

Pb₃O₄+ 8HCl → 3PbCl₂ + Cl₂ + 4H₂O

can be splitted into two reactions namely:

2PbO + 4HCl → 2PbCl2 + 2H2O (acid-base reaction)

+4 –1 +2 0

PbO₂ + 4HCl → PbCl₂ + Cl₂ +2H₂O (redox reaction)

• Since HNO₃ itself is an oxidising agent therefore, it is unlikely that the reaction may occur between PbO₂ and HNO₃. However, the acid-base reaction occurs between PbO and HNO₃ as:

2PbO + 4HNO₃ → 2Pb(NO₃)₂ + 2H₂O