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Q 3121223121.     (i) For each substance listed below, explain its significance in the extraction of aluminium:
(a) Bauxite (c) Cryolite
(b) Sodium hydroxide (d) Graphite.
(ii) Relating to the extraction of aluminium by electrolysis: (a) Give the equation for the reaction
which takes place at the cathode. (b) Explain why it is necessary to renew the anode periodically.
(iii) In order to obtain aluminium, the following inputs are required: Bauxite, sodium hydroxide
and graphite. The aluminium compound in bauxite is aluminium oxide and the main impurity
is iron (III) oxide. Aluminium is obtained by the electrilysis of aluminium oxide dissolved in
cryolite. ( 1 ) When bauxite is treated with sodium hydroxide solution what happens to the (a)
aluminium oxide (b) iron (III) oxide. (2) Name the process used for the purification of bauxite.
(3) Write the equation for the action of heat on aluminium hydroxide. (4) Write the formula of
(iv) Aluminium is extracted from its chief ore, bauxite.
(a) Write three balanced equations for the purification of bauxite by Hall's process.
(b) Name the chemical used for dissolving `Al_2O_3` In which state of subdivision is the chemical
(c) Write an equation for the reaction which takes place at the anode during the extraction of
aluminium by the electrolytic process.
(d) Mention one reason for the use of aluminium in thermite welding.
(v) A to F below relate to the source and extraction of either Zinc or Aluminium.
A: Bauxite, B: Coke, C: Cryolite, D: Froth floatation, E: Sodium hydroxide solution, F: Zinc
(a) Write down the three letters each from the above list which are relevant to - ( 1 ) Zinc
(b) Fill in the blanks using the most appropriate words from A to F : -
( 1 ) The ore from which aluminium is extracted must first be treated with _______ so that pure Aluminium oxide can be obtained .
(2) Pure Aluminium oxide is dissolved in __ to make a conducting solution.
(c) Write the formula of Cryolite.
(vi) Name the compound added to lower the fusion temperature of the electrolytic bath in the
(vii) Write down the word which correctly completes the following sentence: - "By dissolving
aluminium oxide in cryolite a _ [conducting / non-conducting] solution is
(viii) Why is so much graphite required for this electrolytic process. Write the equation for the reaction
which take place at the cathode.
(Provided By a Student and Checked/Corrected by EXXAMM.com Team)