Tag: extraction of aluminium

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

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

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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. 

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

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

  1. Electrolytic reduction

  2. Leaching

  3. Hyfrolysis

  4. Thermal decomposition
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The extraction of aluminium from bauxite involves the Bayer process (leaching) followed by the Hall-Heroult process, which is an electrolytic reduction of alumina. Since the question asks what is involved, and electrolytic reduction is the primary step for obtaining the metal, it is the most specific answer.

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

Aluminium is obtained by.

  1. heating AL2O with iron

  2. heating AL2O3 with coke

  3. electrolysing a solution of AL2O3 in molten cryolite

  4. electrolysing fused AICI3
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Aluminium is commercially produced via the Hall-Héroult process, which involves the electrolytic reduction of alumina (Al2O3) dissolved in molten cryolite (Na3AlF6) to lower its melting point and improve conductivity.

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

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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

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

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

  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 $Al _2O _3$
Reveal answer Fill a bubble to check yourself
D Correct answer
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  $Al _2O _3$

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

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

  1. higher, increase

  2. higher, decrease

  3. lower, increase

  4. lower, decrease
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

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

  1. flux

  2. slag to remove impurities

  3. reducing agent

  4. insulation and does not allow heat to escape
Reveal answer Fill a bubble to check yourself
D Correct answer
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. 
Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

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

  1. lower the melting point of alumina.

  2. increase the electrical conductivity.

  3. minimize the anode effect.

  4. remove the impurities from alumina.
Reveal answer Fill a bubble to check yourself
A,B Correct answer
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.