Select the correct statement for electrolysis of $A l_{2} O_{3}$ by Hall-Heroult process.

Cryolite

N a_{3} [A l F_{6}]

lowers the melting point of

A l_{2} O_{3}

and increases its electrical conductivity.

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Al is obtained at cathode and probably

C O_{2}

at anode.

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Both of the above statements are correct.

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None of the above statements are correct.

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Solution

The correct option is C Both of the above statements are correct.
In the extraction of aluminium by electrolytic process, alumina $A l_{2} O_{3}$ is used along with fluorspar and cryolite.
Cryolite reduces the melting temperature of the mixture and also acts as a solvent and helps dissolve $A l_{2} O_{3}$ .
Cryolite: $N a_{3} [A l F_{6}]$
$N a_{3} [A l F_{6}] \to 3 N a F + A l F_{3}$
$N a F$ and $A l F_{3}$ , both are ionic compounds, and ionise to give ions. This increases the electrical conductivity and lowers the melting point of $A l_{2} O_{3}$ .
At cathode: $A l^{3 +} + 3 e^{-} \to A l$
At anode: $C (s) + O^{2 -} (m e l t) \to C O (g) + 2 e^{-}$
$C (s) + 2 O^{2 -} (m e l t) \to C O_{2} (g) + 4 e^{-}$

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Similar questions

Q. In electrolysis of

A l_{2} O_{3}

by Hall-Heroult process, _____________.

Q. 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

C O_{2}

are produced at the cathode.

You are given an Ellingham diagram (deliberately not shown). It is given that for almost all practically achievable temperatures, the $F e \to F e_{2} O_{3}$ line lies above the $A l \to A l_{2} O_{3}$ line and $Δ_{f} G^{\circ}$ for both $A l_{2} O_{3}$ and $F e_{2} O_{3}$ are negative. Which of the following statements is/are true?

Q. Consider the following statements regarding electric fuse wire
1.It has low melting point
2.It has very high specific resistance
3.it is connected in parallel with the electric circuit
Which of the statements given above is/are correct?

Q. Consider the following statements.
1. The boiling point of liquid increases on increasing the pressure on the free surface of the liquid.
2. On heating the solid substance if the volume of the substance increases, then by the application of pressure its melting point increases.
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Select the correct statement for electrolysis of Al2O3 by Hall-Heroult process.

Select the correct statement for electrolysis of $A l_{2} O_{3}$ by Hall-Heroult process.