Explanation:
A= Mercury (ll) oxide
B= Mercury and Oxygen
This is an oxidation-reduction (redox) reaction:
2 HgII + 4 e- ā 2 Hg0
(reduction)
2 O-II - 4 e- ā 2 O0
(oxidation)
HgO is an oxidizing agent, HgO is a reducing agent.
