Home · IGCSE Chemistry 0620 · Metals · Extracting aluminium by electrolysis · Practice
IGCSE · Practice questions · Extracting aluminium by electrolysis

Bauxite to metal.

Six original Cambridge-style questions on extracting aluminium by electrolysis.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Aluminium down, oxygen up.

01
Recall
[2 marks]

Name the ore from which aluminium is extracted, and the compound it is purified to.

  • Bauxite. ✓
  • Aluminium oxide, Al2O3. ✓
02
Explain
[2 marks]

Explain why aluminium oxide is dissolved in molten cryolite before electrolysis.

  • Aluminium oxide has a very high melting point (over 2000 °C). ✓
  • Dissolving it in molten cryolite allows electrolysis at a lower temperature (about 950 °C), saving energy. ✓
03
Recall
[2 marks]

Name the product at each electrode.

  • Cathode: aluminium. ✓
  • Anode: oxygen. ✓
04
Explain
[2 marks]

Explain why the carbon anodes have to be replaced regularly. Include an equation.

  • Oxygen is produced at the hot anodes and reacts with the carbon. ✓
  • C + O2 → CO2, so the anodes are gradually burned away. ✓
05
Recall
[2 marks]

(Extended) Write the half-equations for the reactions at the cathode and the anode.

  • Cathode: Al3+ + 3e− → Al ✓
  • Anode: 2O2− → O2 + 4e− ✓
06
Explain
[2 marks]

Suggest two reasons why aluminium extraction plants are often built near hydroelectric power stations.

  • The process needs very large amounts of electricity. ✓
  • Hydroelectric power supplies cheap electricity (and produces no carbon dioxide from fuel burning). ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.