Chlorine is the second most reactive element in the group of the halogens. It
is extracted from sodium chloride in a process known as the electrolysis of brin.
However, in a laboratory Chlorine may be easily obtained through the oxidation
of concentrated hydrocholric acid with potassium manganate (VII).
Chlorine is the third most electronegative element after fluorine and oxygen.
Its main oxidation state is -1, however, when it reacts together with fluorine
and oxygen it forms positive oxidation states. Some examples are sodium chlorate
(I) and sodium hypochlorite NaOCl, where chlorine has Ox = +1. Nevertheless,
Chlorine can reach oxidation states of +5.
Test for Chlorine:
The test for Chlorine is based upon its strong oxidizing characterisitcs.
Chlorine is a very strong bleach. Used on moist litmus paper, it reacts
making th elatter go completely colourless. If blue litmus is used, it turns
briefly red before reaching the colourless state.
Chlorine is more reactive than Bromine and Iodine and will as a result
oxidize them when found in a compound. The solution will turn yellow-brown
when bromides are oxidized to Bromine, and dark brown when iodides are
oxidized to Iodine.
When silver nitrate is added to chlorine, it forms an insoluble compound.
Therefore, if chlorine is present a white precipitate is formed in this
reaction.
Uses of Chlorine:
Water Treatment: Chlorine is widely used as a means to sterilize
water for drinking. Its use has been one of the most important causes of the
disappearance of illnesses such as cholera and typhoid. It is also sometimes
used in sewage systems.
Organochlorine manufacture: Chlorine reacts with many organic
compounds to form useful subsdtances. For instance, it is used in pesticides.
However, organchloro compounds are in decline since they have been
discovered to be realted to problems of toxicity and the green-house effect.
Manufacture of Hydrocholoic Acid: HCl is one of the cheapest acids,
and is widely used as a general-purpose acid. The acid is used to make metal
chlorides, to clean the surfaces of metals before electroplating and to make
corn syrup and glucose from corn starch.
