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In the electrolytic method of obtaining ...

In the electrolytic method of obtaining aluminium from purified bauxite, cryolite is added to the charge in order to

A

minimise the heat loss due to radiation

B

protect aluminium produced from oxygen

C

dissolve bauxite and render it conductor of electricity

D

lower the melting point of bauxite.

Text Solution

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The correct Answer is:
D
(i) Pure alumina is a bad conductor of electricity
(ii) The fusion temperature of pure alumina is about `2000^(@)C` and at this temperature when the electrolysis is carried of fused mass, the metal formed evaporates as the boiling point of aluminium is `1800^(@)C`.The above difficulties are overcome by using a mixture of alumina, cryolite and fluorspar.
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