Tag: metallurgy of aluminium

Questions Related to metallurgy of aluminium

Function of adding cryolite in the extraction of aluminium from pure alumina is?

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. to increase the fusion temperature

  2. to decrease the conductivity of alumina

  3. to decrease the fusion temperature and increase the electrical conductivity

  4. none of these

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Correct Option: C
Explanation:

As Alumina has high melting point and low conductivity, Cryolite is added to reduce melting point and flour spar is added in small amount to increase electrical conductivity. 

Aluminium is extracted by the electrolysis of:

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. Bauxite

  2. Alumina

  3. Alumina mixed with molten cryolite

  4. Molten cryolite

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Correct Option: C
Explanation:

In the extraction of aluminium by electrolytic process alumina $Al _2O _3$ is used along with molten fluorspar and cryolite.


Hence, the correct option is $C$

Which of the following is / are involved in extraction of aluminium from bauxite?

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. Electrolytic reduction

  2. Leaching

  3. Hyfrolysis

  4. Thermal decomposition

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Correct Option: A

Aluminium is obtained by.

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. heating AL2O with iron

  2. heating AL2O3 with coke

  3. electrolysing a solution of AL2O3 in molten cryolite

  4. electrolysing fused AICI3

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Correct Option: D

All the statements are correct.
(i) In gold Schmidt thermite process aluminium acts as a reducing agent
(ii) Mg is extracted by electrolysis of aq. solution of $MgCl _{2}$
(iii) Extraction of Pb is possible by smelting
(iv) Red bauxite is purified by Serpeck's  Method

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. True

  2. False

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Correct Option: A
Explanation:

Option A & C are correct.
But Serpeck's  Method is used to purify white bauxite.
and
Mg is extracted by electrolysis of anhydrous $MgCl _{2}$.

The cathode used in the electrolytic cell during aluminium extraction is made of ____________.

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. aluminium

  2. carbon Iining

  3. iron

  4. steel

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Correct Option: B
Explanation:

The cathode used in the electrolytic cell during aluminium extraction is graphite lining (carbon lining).

The constituents of the electrolyte for the extraction of aluminium is ____________.

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. 40 parts cryolite + 40 parts fluorspar + 20 parts pure $Al _2O _3$

  2. 60 parts cryolite + 30 parts fluorspar + 10 parts pure $Al _2O _3$

  3. 30 parts cryolite + 30 parts fluorspar + 40 parts pure $Al _2O _3$

  4. 60 parts cryolite + 20 parts fluorspar + 20 parts pure $Al _2O _3$

Show answer
Correct Option: D
Explanation:

Pure alumina melts at about $2000^oC$ and is a bad conductor of electricity. If fused cryoliteand fluorspar is added, the mixture melts at $900^oC$ and $Al _2O _3$ becomes a good conductorof electricity.
Electrolyte: 60 parts cryolite + 20 parts fluorspar + 20 parts pure  $Al _2O _3$

Cryolite, $Na 3AlF _6$ is added to $Al _2O _3$ in Hall-Heroult process to ___ m.p. and to ___________ electrical conductivity.

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. higher, increase

  2. higher, decrease

  3. lower, increase

  4. lower, decrease

Show answer
Correct Option: C
Explanation:

In the Hall–Héroult process alumina, $Al _2O _3$, is dissolved in molten cryolite, $Na _3AlF _6$ to lower it's melting point for easier electrolysis. It also increases conductivity of the solution.

A layer of coke is spread over bayzite during extraction of aluminium. This acts as an ____________.

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. flux

  2. slag to remove impurities

  3. reducing agent

  4. insulation and does not allow heat to escape

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Correct Option: D
Explanation:
A layer of powdered coke is spread over bauxite (molten electrolyte) during extraction of aluminium. This acts as an insulation and does not allow heat to escape and prevents oxidation. 

In the electrolysis of alumina, cryolite is added to ______________.

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. lower the melting point of alumina.

  2. increase the electrical conductivity.

  3. minimize the anode effect.

  4. remove the impurities from alumina.

Show answer
Correct Option: A,B
Explanation:

The electrolysis of pure alumina faces some difficulties. Pure alumina is a bad conductor of electricity. The fusion temperature of pure alumina is about 2000$^{\circ}$C and at this temperature when electrolysis is carried out on the fused mass, the metal formed vaporizes, as the boiling point of aluminium is 1800$^{\circ}$C. These difficulties are overcome by using a mixture containing alumina, cryolite $(Na _3,AlF _6)$, and fluorspar $(CaF _2,)$. But the addition of cryolite do not minimize the anode effect and do not remove the impurities from alumina.