Core
Reactions: Balancing Redox Equations
Slide 17 of 29
Oxidation of a
species with oxygen
Something else that should have been evident from your
experiment on redox reactions in acidic medium is that, in
the case of polyatomic ions with oxygen, the reduced species
has fewer oxygen than the oxidized species.
That is oxidizing agents have more oxygen than reducing
agents.
–NO3- when reduced forms NO2-
–SO42- when reduced forms SO32-
–Cr2O72- when reduced forms Cr3+
–MnO4- when reduced forms Mn2+ (or MnO2)
By the same token,
–NO2- when oxidized converts into NO3-
–SO32- when oxidized converts into SO42- etc.
Common laboratory oxidizing agents are KNO3,
KClO, KMnO4 and KCr2O7.
As a matter of fact, any compound with a relatively large number
of oxygen behave as oxidizing agents, such as NH4NO3,
NH3Cr2O7,
KClO3, KClO4 etc.