Chlorine
(Castner-Kellner’s)
Introduction
Chlorine plays an important role in
industries. Therefore to fulfill the demands, chlorine is manufactured on large
scale. It is prepared by the electrolysis of aqueous solution sodium chloride,
this process is known as Castner-Kellner’s Process and it is carried out in
Castner-Kellner’s Cell.
Construction of Castner-Kellner’s Cell
The Castner-Kellner’s cell consist of
a steel tank which contain Hg flows from right to left in the cell and is
connected with the negative terminal of the battery therefore it acts as
cathode. The cell is filled with saturated aqueous solution of NaCl, which also
flows in the same direction as Hg. Some graphite rods are dipped into the
solution of NaCl. These rods connected with positive terminal of the battery
therefore act as anode.
Working Of Castner-Kellner’s Cell
When the electric current is passed
through the cell. The sodium ion and chloride ion migrates towards their
respective electrodes. Chlorine ion moves towards anode, loses its electron and
converts into chlorine gas. The free chlorine gas comes out of the tube at the
top of the cell. The sodium ion migrates towards cathode gains electrons and
converts into sodium metal. The sodium is dissolved in Hg to form sodium
amalgum which comes out with the flow of Hg from the cell.
NaCl <—-> Na+ + Cl-
Na+ + e- —-> Na0 (At Cathode)
2Cl —-> Cl2↑ + 2e (At anode)
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