Mention a few difficulties involved in the extraction of sodium from fused sodium chloride.
Answers
The following are the reasons why sodium cannot be formed from fused chloride,
(i) Sodium chloride has a melting point at 1074 K. It is very difficult to attain this temperature and maintain it.
(ii) Since sodium boils at 1165 K, at this temperature of electrolysis, the metal gets liberated. Then the liberated metal gets vaporized.
(iii) Also the molten sodium forms a colloidal solution (a metallic fog) with the fused sodium chloride.
(iv) Since at high temperature, the products sodium and chlorine of electrolysis corrodes the cell.
Answer:
ANSWER
On industrial scale sodium metal is extracted by "Down's Process".
PRINCIPLE:Down's Process is based on the electrolysis of fused NaCl.
CONSTRUCTION OF DOWN'S CELL:
Down's cell consists of a rectangular container of steel.
Inside of the tank is lined with firebricks.
Anode is a graphite rod which projects centrally up through the base of the cell.
Cathode is a ring of iron, which surrounds the anode.
The anode and cathode are separated from each other by a cylindrical steel gauze diaphragm so that Na and Cl
2
are kept apart.
A bell like hood is submerged over the anode.