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In the electrolysis of alumina, cryolite...

In the electrolysis of alumina, cryolite is added to

A

lower the mp of alumina

B

Increases the electrical conductivity

C

Minimize the anode effect

D

Remove impurities from alumina

Text Solution

Verified by Experts

The correct Answer is:
A, B
Because of high mp `(2050^(@)C)` , pure alumina cannot be electrolysed. Hence a mixture of of alumina, cryolite (mp. `1000^(@)C`) and calcium fluoride (to lower the temperature of the melt) is electrolysed at about `900^(@)C`. The function of cryolite is to increases the electrical conductivity of the electrolyte and to lower the temperature of the melt.
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Knowledge Check

  • In the electrolusis of alumina. Cryolite is absorbed to

    A
    Lower that melting point of alumia
    B
    Increase the electical condivity
    C
    Minimise the anode effect
    D
    Remove impurities form alumia

  • In the electrolysis of alumina , cryolite and CaF_(2) are added to

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    increase the emf of cell
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    decrease the emf of cell
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    decrease the melting point
    D
    Both (b) and (c)

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    A
    to dissolve alumina
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    to increase ionisation of alumina
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    tp increase the fusion temperature of alumina
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