CIE iGCSE Co-Ordinated Science C9.6 Extraction of metals Exam Style Questions Paper 4
Question
Aluminium is extracted by electrolysis from the ore bauxite that contains aluminium oxide, Al$_{2}$O$_{3}$.
The equation for the overall reaction is
2Al$_{2}$O$_{3}$(l) 4Al(l) + 3O$_{2}$(g)
(a) A scientist electrolyses 81.6g of aluminium oxide.
Calculate the maximum mass of aluminium extracted from the aluminium oxide.
Show your working.
[A$_{r}$ : Al, 27; O, 16]
mass of aluminium = ……………………………………………… g
(b) At the anode oxide ions, O$^{2}–$, form oxygen molecules.
2O$^{2}$– O$_{2}$ + 4$^{e}–$
State if this reaction is oxidation or reduction.
Explain your answer.
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(c) Construct the ionic half‐equation for the reaction at the cathode.
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(d) Iron can be extracted from iron oxide by heating the iron oxide with carbon.
Explain why aluminium cannot be extracted from aluminium oxide using this method.
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(e) Fig. 11.1 shows metallic bonding.
Use Fig. 11.1 to explain why metals conduct electricity.
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▶️Answer/Explanation
Ans :
11(a) relative molecular mass of Al$_{2}$O$_{3}$ = 102 ;
$\left ( \frac{54\times 81.6}{102}= \right )43.2(g);$
11(b) oxidation
and
electrons are lost ;
11(c) $Al ^{ 3+} + 3^{e–} → Al $
1 mark for correct symbols ;
1 mark for correctly balanced electrons ;
11(d) idea that aluminium is more reactive than carbon / ORA ;
11(e) has free electrons ;
which can move throughout/in (the metal) ;