In order to obtain aluminium, the following inputs are required: Bauxite, sodium hydroxide and graphite.
When bauxite is treated with sodium hydroxide solution what happens to the:
$(a)$ aluminium oxide (aluminium compound in bauxite).
$(b)$ iron $(I I I)$ oxide (main impurity).
Name the process used for the purification of bauxite.
Write the equation for the action of heat on aluminium hydroxide.
Write the formula of cryolite.

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Solution

(A) Bauxite with $N a O H$
(a) Aluminium oxide dissolves in sodium hydroxide to form sodium aluminate.
(b) Iron oxide is not solvable in $N a O H$ & is removed.
(B) The process is known as Baeyer's process.
(C) The action of heat on $A l (O H)_{3}$ -
$2 A l (O H)_{3} Δ - \to A l_{2} O_{3} + 3 H_{2} O$
(D) Formula of cryolite is $N a_{3} A l F_{6}$ .

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In order to obtain 1 tonner of aluminium, the following inputs are required. 4 tonnes of bauxite, 150 kg of sodium hydroxide and 600 kg of graphite. The aluminium compound in bauxite is aluminium oxide and the main impurity is Iron (III) oxide. Aluminium is obtained by the electrolysis of aluminium oxide dissolved in cryolite.

(a) When bauxite is treated with sodium hydroxide solution, what happens to:

(i) the aluminium oxide,

(ii) the iron (III) oxide?

(b) (i) Name the process used for the purification of bauxite.

(ii) Write the equation for the action of heat on aluminium hydroxide.

(ii) Write down the word which correctly completes the following sentence.By dissolving aluminium oxide in cryolite a ..........(conducting/non conducting) solution is produced.

(iii) Why is so much graphite required for the electrolytic process?

(iv) Write the equation for the reaction which takes palace at cathode.

Q. In order to obtain one tonne of aluminium, the following inputs are required:
4 tonnes of bauxite, 150 kg of sodium hydroxide and 600 kg of graphite.
The aluminium compound in bauxite is aluminium oxide and the main impurity is iron (III) oxide. Aluminium is obtained by the electrolysis of aluminium oxide dissolved in cryolite.
(a) When bauxite is treated with sodium hydroxide solution, what happens to:
(i) the aluminium oxide?
(ii) the iron (III) oxide?
(b) (i) Name the process used for the purification of bauxite.
(ii) Write the equation to show the action of heat on aluminium hydroxide.
(c) (i) Write the formula of cryolite.
(ii) Write down the word which correctly completes the following sentence:
"By dissolving aluminium oxide in cryolite, a __________ (conducting/non-conducting) solution is produced.
(iii) Why is so much graphite required for this electrolytic process?
(iv) Write the equation for the reaction which takes place at the cathode.
(d) In construction work, why is the alloy of aluminium, duralumin used rather than pure aluminium.

Q. When bauxite is treated with sodium hydroxide solution what happens to the iron

(I I I)

oxide (main impurity).

Explain the significance of the following in the extraction of aluminium.
(i) Bauxite
(ii) Sodium hydroxide
(iii) Cryolite
(iv) Graphite

For each substance listed below, explain its significance in the extraction of aluminium:

(a) Bauxite, (b) Sodium hydroxide,

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(A) Bauxite with NaOH(a) Aluminium oxide dissolves in sodium hydroxide to form sodium aluminate.(b) Iron oxide is not solvable in NaOH & is removed.(B) The process is known as Baeyer's process.(C) The action of heat on Al(OH)3-2Al(OH)3Δ−→Al2O3+3H2O(D) Formula of cryolite is Na3AlF6.