Extraction of Metals Exam Questions
Practice IGCSE Chemistry exam questions on extraction of metals. Covers extraction by carbon reduction, electrolysis, choosing the extraction method, the blast furnace, and recycling metals with mark schemes and examiner notes.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
These questions cover extraction of metals. Write full answers before checking.
Question 1 (3 marks, Core)
Explain why aluminium is extracted by electrolysis but iron is extracted by heating with carbon.
Mark scheme
- Aluminium is above carbon in the reactivity series, so carbon cannot reduce aluminium oxide [1]
- Electrolysis is needed because it uses electrical energy, which is powerful enough to decompose the very stable Al2O3 [1]
- Iron is below carbon in the reactivity series, so carbon (as coke) can reduce iron oxide. This is cheaper than electrolysis [1]
Examiner note: The reactivity series is the key: metals above C need electrolysis (expensive); metals below C can be reduced by C (cheaper). The position of carbon in the series is the dividing line.
Question 2 (4 marks, Core)
Describe the main chemical reactions occurring in the blast furnace during the extraction of iron.
Mark scheme
- Coke (carbon) burns in hot air: C + O2 → CO2 [1]
- CO2 reacts with more coke to form carbon monoxide: CO2 + C → 2CO [1]
- Carbon monoxide reduces iron ore (iron(III) oxide): Fe2O3 + 3CO → 2Fe + 3CO2 [1]
- Limestone (CaCO3) decomposes and the calcium oxide removes impurities (sand/silica) by forming slag: CaO + SiO2 → CaSiO3 [1]
Examiner note: The reducing agent is carbon monoxide (CO), not carbon directly. The sequence is: C → CO2 → CO → reduces Fe2O3. Limestone removes acidic impurities. Molten iron collects at the bottom of the furnace.
Question 3 (3 marks, Supplement)
Write balanced equations for the reduction of the following metal oxides by carbon:
(a) Zinc oxide (ZnO) (1)
(b) Copper oxide (CuO) (1)
(c) Lead oxide (PbO) (1)
Mark scheme
(a) 2ZnO + C → 2Zn + CO2 [1]
(b) 2CuO + C → 2Cu + CO2 [1]
(c) 2PbO + C → 2Pb + CO2 [1]
Examiner note: In each case, carbon removes oxygen from the metal oxide. This is a redox reaction: the metal oxide is reduced (loses oxygen) and carbon is oxidised (gains oxygen). Carbon acts as the reducing agent.
Question 4 (4 marks, Supplement)
Aluminium is extracted from purified aluminium oxide (alumina) by electrolysis.
(a) Why must the alumina be dissolved in molten cryolite? (1)
(b) Write the half equation at the cathode. (1)
(c) Write the half equation at the anode. (1)
(d) Explain why the carbon anodes need to be replaced regularly. (1)
Mark scheme
(a) To lower the melting point of alumina (from about 2050 degC to about 950 degC), reducing the energy cost [1]
(b) Al3+ + 3e- → Al [1]
(c) 2O2- → O2 + 4e- [1]
(d) The oxygen produced at the anode reacts with the carbon electrodes at the high temperature, forming CO2, so the anodes burn away [1]
Examiner note: The high cost of aluminium extraction is due to the large amount of electricity needed. The process runs continuously. Recycling aluminium saves about 95% of the energy needed to extract it from ore.
Question 5 (3 marks, Core)
State three reasons why recycling metals is beneficial.
Mark scheme
Any three from:
- Conserves finite/non-renewable ore reserves [1]
- Saves energy (recycling uses much less energy than extracting from ore) [1]
- Reduces the amount of waste going to landfill [1]
- Reduces environmental damage from mining (habitat destruction, noise, dust) [1]
- Reduces greenhouse gas emissions (less energy = less CO2 from burning fossil fuels) [1]
Examiner note: Each reason must be distinct. “Saves money” is acceptable if linked to energy savings. “Good for the environment” is too vague — specify which aspect of the environment.
Question 6 (3 marks, Core)
Complete the table to show the method used to extract each metal.
| Metal | Position in reactivity series | Extraction method |
|---|---|---|
| Potassium | Very reactive | ? |
| Iron | Moderately reactive | ? |
| Gold | Very unreactive | ? |
Mark scheme
- Potassium: electrolysis (of molten compound) [1]
- Iron: reduction with carbon/coke (in a blast furnace) [1]
- Gold: found native/uncombined — physical separation (panning, filtration) [1]
Examiner note: The three categories are: very reactive metals → electrolysis; moderately reactive metals → reduction with carbon; unreactive metals → found as the element. This directly mirrors the reactivity series.
Question 7 (4 marks, Supplement)
A student heats copper oxide with carbon powder in a crucible. After heating, she observes a pink-brown solid and a gas that turns limewater milky.
(a) Write the equation for the reaction. (1)
(b) Identify the pink-brown solid and the gas. (1)
(c) Explain why this method works for copper but not for calcium. (2)
Mark scheme
(a) 2CuO + C → 2Cu + CO2 [1]
(b) Pink-brown solid = copper; gas = carbon dioxide [1]
(c) Copper is below carbon in the reactivity series, so carbon is reactive enough to remove oxygen from copper oxide [1]. Calcium is above carbon in the reactivity series, so carbon cannot reduce calcium oxide — electrolysis is needed instead [1].
Examiner note: The limewater test confirms CO2 production. This lab experiment demonstrates the principle of extraction by carbon reduction. It is a common practical that links to the blast furnace theory.
What to revise if you scored below 5
If the link between reactivity and extraction method was unclear, draw the reactivity series and mark where carbon sits. Everything above C needs electrolysis; below C can be reduced by carbon. If blast furnace equations were difficult, learn the four key equations in order. Revisit the extraction of metals notes.
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