ElectrolysisHow It Works

The Hall-Héroult Process — Step by Step

Part of Electrolysis of Aluminium · GCSE GCSE Chemistry revision

This how it works covers The Hall-Héroult Process — Step by Step within Electrolysis of Aluminium for GCSE Chemistry. Revise Electrolysis of Aluminium in Electrolysis for GCSE Chemistry with 21 exam-style questions and 14 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 5 of 13 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 5 of 13

Practice

21 questions

Recall

14 flashcards

⚙️ The Hall-Héroult Process — Step by Step

Mine bauxite ore and purify it to extract pure aluminium oxide (Al₂O₃)
Dissolve Al₂O₃ in molten cryolite at ~950°C (cryolite lowers melting point, saving energy and money)
Pass DC electricity through the molten mixture using carbon electrodes
At the CATHODE (−): Al³⁺ ions gain 3 electrons → molten aluminium metal sinks to the bottom of the cell
At the ANODE (+): O²⁻ ions lose 2 electrons → oxygen gas bubbles off
Oxygen reacts with carbon anodes: C + O₂ → CO₂ (anodes burn away and need replacing)
Tap off molten aluminium from the bottom of the cell

Keep building this topic

Read this section alongside the surrounding pages in Electrolysis of Aluminium. That gives you the full topic sequence instead of a single isolated revision point.

Half Equations — Must Know!Key Definitions The Metal That Changed History The Hall-Heroult Cell — Click to Explore

Practice Questions for Electrolysis of Aluminium

Why is aluminium extracted by electrolysis rather than by reduction with carbon?

A. Aluminium is less reactive than carbon
B. Aluminium is more reactive than carbon
C. Aluminium does not form ions
D. Carbon reacts with aluminium to form carbides

1 markfoundation

Explain why aluminium is extracted by electrolysis rather than by reduction with carbon.

2 marksstandard

Quick Recall Flashcards

What does OIL RIG stand for?

Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons). At the Anode = Oxidation (loss). At the Cathode = Reduction (gain).

Why do the carbon anodes need replacing regularly?

At 950°C, the oxygen produced at the anode reacts with the hot carbon: C + O₂ → CO₂. The carbon is gradually burned away, so the anodes must be replaced periodically.

21 questions on Electrolysis of Aluminium — practise free

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Half Equations — Must Know!

Key Definitions