Tag: metallurgy of aluminium

Questions Related to metallurgy of aluminium

$NaAlO 2$ on hydrolysis gives ________.

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

  1. $NaOH$

  2. $Al _2O _3$

  3. both $A$ and $B$

  4. none of the above

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Correct Option: C
Explanation:

$NaAlO _2$ on hydrolysis gives sodium hydroxide and $Al _2O _3$.

$2NaAlO _2 + H _2O \rightarrow Al _2O _3 + 2NaOH$

During electrolysis of aluminium, which of the following substance is used as an electrolyte?

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

  1. $Al _2O _3$

  2. $Al _2O _3, Na _3AlF _6$

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

  4. None of the above

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Correct Option: C
Explanation:

The substance which is used as an electrolyte during electrolysis of aluminium is $Al _2O _3, Na _3AlF _6, CaF _2$.

Anodic product in the electrolytic reduction of alumina:

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

  1. $CO _2, O _2$

  2. $O _2$

  3. $F _2$

  4. $O _2,F _2$

Show answer
Correct Option: B
Explanation:

Ionization of Alumina in Electrolytic refining.

$2Al _2O _3\longrightarrow 6O^{-2}+Al^{3+}$
Reaction at cathode
$4Al^{3+}+12e^{-}\longrightarrow 4Al$
Reaction at anode
$6O^{-2}\longrightarrow 3O _2+12e^-$
$O _2$ is released at anode.

The most abundant metal in the earths crust is:

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

  1. silver

  2. aluminium

  3. zinc

  4. iron

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Correct Option: B
Explanation:

Most abundant metal on the earth's crust is Aluminium.

Aluminium is extracted mainly from its principal ore :

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

  1. magnetite

  2. kaolinite

  3. bauxite

  4. haematite

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Correct Option: C
Explanation:

Naturally occurring aluminium is a major component of silicates such as mica and clay. Aluminium is extracted mainly from its principal ore bauxite.

Which of the following statements is correct?
(i) Copper is extracted by hydrometallurgy from low-grade ores.
(ii) In the electrolytic reduction of alumina, graphite is acting as an anode and steel vessel with the lining of carbon acts as an anode.
(iii) In Hall-Heroult process, aluminium is obtained at anode and CO and $CO _2$ are produced at the cathode.

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

  1. (i) only

  2. (i) and (ii) only

  3. (ii) and (iii) only

  4. All of these

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Correct Option: B
Explanation:
$(i)$ Copper is extracted by hydrometallurgy from low-grade ores. It is leached out using acid or bacteria. The solution containing $Cu^{2+}$ is treated with scrap iron or $H _2$.
$Cu^{2+} (aq)+H _2 (g)\longrightarrow Cu (s)+2H^+ (aq)$
$(ii)$ In the electrolytic reduction of alumina. The graphite act as anode and steel with a lining of carbon acts as an anode.
$(iii)$ The process of extracting Aluminium from Alumina $(Al _2O _3)$ by electrolysis is called Hall-Heroult process. In this process Aluminium is produced at cathode which is obtained by outlet, oxygen is released at an anode. It reacts with carbon of anode producing $CO$ and $CO _2$.

Cryolite and fluorspar are mixed with $Al _2O _3$ during electrolysis for extraction of aluminium to:

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

  1. increase the mass of the reaction mixture

  2. get other products at anode like fluorine

  3. lower the melting point and increase the conductivity of the electrolyte

  4. reduce aluminium oxide by cryolite

Show answer
Correct Option: C
Explanation:

In the metallurgy of Aluminium, purified $Al _2O _3$ is mixed with $Na _3AlF _6$ or $CaF _2$ which lowers the melting point of mix and brings conductivity.

In the metallurgy of aluminium:

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

  1. $Al^{3+} $ is oxdised to $Al _{(s)}$

  2. graphite anode is oxidised to carbon monoxide and carbon dioxide

  3. oxidation state of oxygen changes in the reaction at anode

  4. oxidation state of oxygen changes in the overall reaction involved in the process

Show answer
Correct Option: B
Explanation:
The oxidation state of $'O'$ does not change i neither the reaction occurring at the anode or the overall reaction as shown below.
At anode:-$C+{ O }^{ 2- }\longrightarrow CO+2{ e }^{ - };C+2{ O }^{ 2- }\longrightarrow C{ O } _{ 2 }+4{ e }^{ - }$
The released electrons used at cathode and here Graphite  is oxidized to $'CO'$ and $C{ O } _{ 2 }$

Purification of aluminium by electrolytic refining is called:

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

  1. Serpeck's process

  2. Hoope's process

  3. Hall's process

  4. Baeyer's process

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Correct Option: B
Explanation:

Purification of aluminium by electrolytic refining is called Hoope's process. Serpeck, Hall's and Baeyer process are chemical process.

In the extraction of aluminium,
Process X: applied for red bauxite to remove iron oxide (chief impurity)
Process Y: applied for white bauxite to remove Z (chief impurity). 

Then, Process X and impurity Z are:

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

  1. X $=$ Hall - Heroults process & Y$=$ $SiO _{2}$

  2. X $=$ Bayers process and Z $=$ $SiO _{2}$

  3. X $=$ Serpecks process and Y $=$ iron oxide

  4. X $=$ Baeyers process and Y $=$ iron oxide

Show answer
Correct Option: B
Explanation:

Bayer's process is used for beneficiation of red bauxite.
Serpeck's process is used for beneficiation of white bauxite. 
Reaction to remove impurity from white bauxite is:
$SiO _2+2C\rightarrow Si+2CO$ .