Tag: chemistry

Questions Related to chemistry

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.

Cryolite is added to alumina as to lower the fusion temperature and make the mass good conductor of electricity.

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:

Aluminium oxide has a very high melting point (over 2,000C), so it would be expensive to melt it. Instead, it is dissolved in molten cryolite, an aluminium compound with a lower melting point than aluminium oxide. The use of cryolite reduces some of the energy costs involved in extracting aluminium.

Identify the process to which the following reaction belongs : 


$\displaystyle { Al } _{ 2 }{ O } _{ 3 }.{ 2H } _{ 2 }O+{ Na } _{ 2 }{ CO } _{ 3 }\longrightarrow { 2NaAlO } _{ 2 }+{ 2H } _{ 2 }O+{ CO } _{ 2 }$

$\displaystyle { 2NaAlO } _{ 2 }+{ 2H } _{ 2 }O+{ CO } _{ 2 } \underrightarrow { 50-{ 60 }^{ o }C } { Al } _{ 2 }{ O } _{ 3 }.{ 2H } _{ 2 }O+{ Na } _{ 2 }{ CO } _{ 3 }$

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

  1. Hall's process

  2. Baeyer's process

  3. Serpeck's process

  4. None of these

Show answer
Correct Option: A
Explanation:

Hall's Process: (Red bauxite)

Bauxite one + $Na _2CO _3 \xrightarrow{Fused} NaAlO _2$
                                                          $\downarrow $ extracted with water
                                                    Solution
                                                          $\downarrow$ warmed $50^o - 60^oC$
                                                   $CO _2$ is circulated
                                                          $\downarrow$
                                                   $Al(OH) _3 + Na _2CO _3$

How many aluminum smelting plants are there in India?

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

  1. 6

  2. 7

  3. 10

  4. 12

Show answer
Correct Option: B
Explanation:

There are 7 different aluminium smelting plant in India.

Which of the following statement(s) is/are correct"?

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

  1. The chemical processes in the production of steel from haematite ore involve reduction followed by

    oxidation.

  2. In Hall-Heroult process, the electrolyte used is a molten mixture of alumina and cryolite or fluorspar.

  3. Lead is extracted from its chief ore galena by both carbon reduction as well as self reduction,

  4. Haematitic, cassiterite, and argentite are oxide ores.

Show answer
Correct Option: A,B,C
Explanation:

A) In the furnace, first the coke reacts with oxygen in the air blast to produce carbon monoxide(oxidation):$2C+O2\rightarrow 2CO$ The carbon monoxide reduces the iron ore (hematite) to molten iron, becoming carbon dioxide in the process:$3CO + Fe _2O _3\rightarrow 2Fe + 3CO _2$
B) The HallHroult process is the major industrial process for smelting of alumina. It involves dissolving alluminium oxide(allumina) in molten cryolite, and electrolysing the molten salt bath, typically in a purpose-built cell.
C) Lead is extracted from its chief ore galena by both carbon reduction as well as self reduction,
D) Haematitic($Fe _2O _3$),cassiterite ($SnO _2$) and argentite($Ag _2S$).So Haematite and cassiterite are oxide ores but argentite is sulphide ore.Incorrect.
Hence options A,B & C are correct.

Aluminium is extracted from alumina $(Al _2O _3)$ by electrolysis of a molten mixture of:

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

  1. $Al _2O _3 + HF + NaAlF _4$

  2. $Al _2O _3+CaF _2+NaAlF _4$

  3. $Al _2O _3+Na _3AlF _6+CaF _2$

  4. $Al _2O _3+KF+Na _2AlF _6$

Show answer
Correct Option: C
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 aluminum is 1800$^{\circ}$C. 

These difficulties are overcome by using a mixture containing alumina$(Al _2O _3)$, cryolite $(Na _3AlF _6)$, and fluorspar $(CaF _2)$.

Therefore, the correct option is $C$