Question

2ClO3- + 5Hg+ 12H+5Hg2+ + Cl2+ 6H2O In the above redox reaction, use oxidation numbers to identify the element oxidized, the element reduced, the oxidizing agent and the reducing agent?

Answer 1

Oxidation means loss of electrons. In oxidation, oxidation number of species increases.

Reduction means gain of electrons.In reduction, oxidation number of species decreases.

Oxidizing agent is a substance which itself undergoes reduction & oxidizes another substance

Reducing agent is a substance which itself undergoes oxidation & reduces another substance .

Consider reaction, 2 ClO3- + 5 Hg + 12 H+ 5 Hg2+ + Cl2+ 6 H2O

Element	oxidation number on reactant side	oxidation number on product side	Change in oxidation number	conclusion
Cl	+5	0	Decreased by 5 unit	Cl is reduced.
O	-2	-2	No change	Neither oxidized nor reduced.
Hg	0	+2	Increased by 2 unit	Hg is oxidized.
H	+1	+1	No change	Neither oxidized nor reduced.

In above reaction, ClO3- acts as a Oxidizing agent and Hg acts as a reducing agent.