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Aluminum is exteracted from alumine AI(2...

Aluminum is exteracted from alumine `AI_(2)O_(3)` by electrolysis of a molten mixture of :

A

`AI_(2)O_(3) +HF + NaIF_(4)`

B

`AI_(2)O_(3) + CaF_(2) + NaAIF_(4)`

C

`AI_(2)O_(3) + Na_(3)AIF_(6)+ CaF_(2)`

D

`AI_(2)O_(3) +KF + Na_(3)Al_(4)^(2)`

Text Solution

Verified by Experts

The correct Answer is:
c
Electrolysis of pure alumine faces to difficulties : (i) pure `AI_(2)O_(3))` is a bed conductor of electricity , (ii) fusion temperature of pure alumina is about `2000^(@)C` and at this temperature (when fused mass is electrolyzed) the metal found vaperizes as the boiling point of `AL` is `1800 ^(@)C` .The above difficulties are overcomed (hall- Heroult process) by using a mixture `AI_(2)O_(3))` cryolite`(Na_(3)AIF_(6))` and flursoar `(CaF_(2))` in the ratio of `20 : 40: 20` .The fusion temperature mixture is `900^(@)C` and it is good conductor of electricity .
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