Answer to Question #201165 in Chemistry for Mark

Question

Balance the reactions below using the change in oxidation number method

1.     PbO₂ + HBr – PbBr₂ + O2 + H₂O

2.     KBr + KClO₂ + H₂SO₄ – Br₂ + KCl + K₂SO₄ + H₂O

Answer 1

The balanced reactions are:

1.     2PbO₂ + 4HBr –> 2PbBr₂ + O₂ + 2H₂O

Pb: reduced, gained two electrons, Pb⁴⁺ --> Pb²⁺

O: oxidized, lost two electrons, O^2- --> O⁰

2.     4KBr + KClO₂ + 2H₂SO₄ –> 2Br₂ + KCl + 2K₂SO₄ + 2H₂O

Cl: reduce, gained four electrons, Cl³⁺ --> Cl^1-

Br: oxidized, lost one electron, Br^1- --> Br⁰