Oxidation reactions are common events
in everyday life :
Example- combustion of fossil fuel,
Corrosion of metals,
Dry cells and accumulators,
Metabolism of nutrients in human
Photosynthesis in green plants
Redox reactions are electron transfer reactions.
The process may involve the complete transfer of
electrons to form ionic bonds or only a partial
transfer or shift of electrons to form covalent bonds.
In terms of electronic concept, oxidation is the
process which involves loss of electrons whereas
reduction is the process which involves gain of
Oxidation is the
loss of electrons by
a particle in a
in an increase in
Ared – n e- -> Aox
Reduction is the
gain of electrons by
a particle in a
reaction that results
in a decrease in the
BOX + n e- -> Bred
Balancing redox reactions
Describing the overall electrochemical
reaction for a redox process requires a
balancing of the component half-reactions
for oxidation and reduction. In general, for
reactions in aqueous solution, this involves
adding H+, OH−, H2O, and electrons to
compensate for the oxidation changes.
2Al + 6HCl → 2AlCl3 + 3H2
2Al → 2Al3+ + 6e- (oxidation)
6e- + 6H+ → 3H2 (reduction)
Al is getting oxidized to 2Al3+. As all metals are
reducing agents & 6H+ gets reduced to 3H2.
Therefore HCl is the oxidizing agent.
Name the substance oxidized, reduced,
oxidizing agent and reducing agent in the
i. 3MnO2 + 4Al → 3Mn + 2Al2O3
a) MnO2 has lost oxygen to form Mn. Hence MnO2 has been
b) Al has gained oxygen to form 2Al2O3. Hence, Al has been
c) MnO2 is the oxidizing agent.
d) Al is the reducing agent.
ii. 2Na +Cl2 → 2NaCl
a) Sodium loses electron to form Na+. Hence, sodium has been
b) Chlorine gains electrons to form Cl-. Hence, chlorine has been
c) Sodium is the reducing agent..
d) Chlorine is the oxidizing agent..
iii. Cu + 2AgNO3 → Cu(NO3)2 + 2Ag
a) Copper has lost electrons to form Cu2+. Hence, copper has
been oxidized &, therefore, is a reducing agent..
b) AgNO3 (Ag+ ion) gains electron to form Ag. Hence, AgNO3
has been reduced &, therefore, is an oxidizing agent..