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In the electrolysis of alumina, cryolite...

In the electrolysis of alumina, cryolite is added to

A

Lower the melting point of alumina

B

Increase the electrical conductivity

C

Minimise the anode effect

D

Remove the impurities from alumina

Text Solution

Verified by Experts

The correct Answer is:
A, B
The electrolysis of pure alumina faces some difficulties. Pure alumina is a bad conductor is of electricity. This fusion temperature of pure alumina is about `2000^@C`, and at this temperature, when the electrolysis is carried out on the fused mass, the metal formed vaporises as the boiling point aluminium is `1800^@ C`. These difficulties are overcome by using a mixture containing alumina, cryolite `(Na_(3)AlF_(6))`, and fluorpar `(CaF_(2))`.
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Explain the following (i) Excess of carbon is added to zinc metallurgy. (ii) In the elctrolysis of alumina, cryolite is added to alumina. (iii) Coke does not cause reduction of Al_(2)O_(3) . (iv) Gold is soluble in aquaregia, silver is not.

Electrolysis of alumina is done.

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

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

  • In the electrolysis of alumina, it is mixed with cryolite ( Na_(3)AIF_(6)) and fluorspar (CaF_(2)) in the ratio 20: 40 : 20. The function of cryolite and fluorspar is

    A
    to dissolve alumina
    B
    to increase ionisation of alumina
    C
    tp increase the fusion temperature of alumina
    D
    to decrease the fusion temperature of alumina and to make it good conductor of electricity

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    In the electrolysis of molten alumina during the manufacture of aluminium:

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