Key concepts
1. Reactions that involve the transfer of one or more electrons from one reactant to another
are called oxidation – reduction reactions. Oxidation is the process whereby a
reactant loses one or more electrons.Reduction is the opposite process whereby a reactant
gains one or more electrons. Simple meaning of oxidation reaction would be
an addition of oxygen to a substance. Reduction reaction would mean removal of oxygen from
a substance. Certain reactions where in hydrogen is removed, are also grouped as
oxidation reactions. Similarly, if hydrogen is added, these reactions are called reduction
reactions.
2. Valency is the combining capacity of an element and depends on the availability of free
electrons, especially in outer orbital of the atom. The oxidation number of an
element represents the numerical value(valency) and sign of charge on the atom of an
element, when it is in the form of an ion. The oxidation state of a free (i.e.
uncombined) element is zero. Increase in oxidation number is termed as oxidation. Decrease in
oxidation number is termed as reduction.
3. A substance which brings out oxidation of another substance, is called as an oxidizing agent
or an oxidant. Oxidizing agent is also defined as a substance, which forces
another substance to lose electrons and in turn it gains the electrons. Substances, which force
another substance to gain electrons and it self lose them, are called
reducing agents or reductant.
4. lon electron method is suitable method to balance a redox reaction equation. In this method
redox reactions are split into two half reactions - an oxidation half reaction
and a reduction half reaction. Since the number of electrons gained is equal to the number of
electrons lost the two half reactions must made equal, then the
balanced reactions are added to get an overall reaction.
5. Many reactions that we come across in our daily life involve a redox process. For example
redox reactions involved in, Photography, Combustion, dry cell batteries
etc.
6. Photosynthesis is a redox reaction. The overall equation for the process may be expressed
as: 600 + 6H2O colegial, CH4 205 + 60, In the above process carbon dioxide(CO2) is
reduced to glucose(C8H120g) and water is oxidized to oxygen. Combustion of
carbohydrates(glucose) by oxygen to give energy is one of the reaction in metabolism
which is a redox reaction. Bleaching powder liberates hypochlorite ion (OCI - ) in water which is
reduced to chloride ions and hydroxide ions while bleaching a cloth.