ElectrolysisIntroduction

Breaking Free — The Prison Break of Ions

Part of Electrolysis of Molten Compounds · GCSE GCSE Chemistry revision

This introduction covers Breaking Free — The Prison Break of Ions within Electrolysis of Molten Compounds for GCSE Chemistry. Revise Electrolysis of Molten Compounds in Electrolysis for GCSE Chemistry with 21 exam-style questions and 14 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 1 of 11 in this topic. Use this introduction to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 1 of 11

Practice

21 questions

Recall

14 flashcards

📖 Breaking Free — The Prison Break of Ions

Imagine ions as prisoners trapped in a crystal jail. In solid ionic compounds, every single ion is locked in a fixed position by powerful electrostatic forces — they can't move, can't escape, can't do anything. Try to pass electricity through? Nothing happens. The ions are frozen in place! But heat them up until they melt... suddenly the prison walls collapse, the ions are FREE to roam, and electricity can flow!

This is the fundamental reason why solid ionic compounds don't conduct electricity but molten (liquid) ionic compounds DO conduct. The ions must be free to move to carry electrical charge from one electrode to the other.

What happens when we electrolyse molten ionic compounds?

Positive ions (cations) are attracted to the negative cathode
At the cathode, they GAIN electrons → This is REDUCTION
The cations become neutral metal atoms → METAL forms at the cathode
Negative ions (anions) are attracted to the positive anode
At the anode, they LOSE electrons → This is OXIDATION
The anions become neutral atoms/molecules → NON-METAL forms at the anode

The beautiful simplicity of molten electrolysis: There are only TWO types of ion present (the metal cation and the non-metal anion), so predicting products is straightforward:

CATHODE: Always the METAL
ANODE: Always the NON-METAL

Example — Molten Lead Bromide (PbBr₂):

Ions present: Pb²⁺ and Br⁻

At cathode: Pb²⁺ + 2e⁻ → Pb (silvery lead metal forms)
At anode: 2Br⁻ → Br₂ + 2e⁻ (orange/brown bromine vapour)

Observations: Silvery liquid metal at cathode, orange/brown fumes at anode

Memory trick for electrodes:
• CATions go to the CAThode (positive ions → negative electrode)
• REDuction at Cathode (both have the letter C in "ReDuCtion"!)
• ANions go to the ANode (negative ions → positive electrode)
• Oxidation at Anode (both are vowels!)

Keep building this topic

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

Electrolysis Cell — Click to Explore How It Works: Ion Migration in Molten Electrolysis Example: Electrolysis of Molten Lead Bromide (PbBr₂)

Practice Questions for Electrolysis of Molten Compounds

Which condition is required for electrolysis to occur with an ionic compound?

A. The ions must be free to move (molten or in solution)
B. The compound must be dissolved in organic solvent
C. The compound must be heated above 1000 °C
D. The compound must contain metallic bonds

1 markfoundation

State the products formed at each electrode when molten lead bromide (PbBr₂) is electrolysed.

2 marksstandard

Quick Recall Flashcards

How do you remember that cations go to the cathode?

CATions → CAThode (both start with CAT) ANions → ANode (both start with AN) Metal at the Minus (cathode is negative), Non-metal at the Plus (anode is positive).

Why does solid lead bromide NOT conduct electricity?

In the solid state, all ions (Pb²⁺ and Br⁻) are held in fixed positions in the ionic lattice by strong electrostatic forces. They cannot move, so they cannot carry electrical charge.

21 questions on Electrolysis of Molten Compounds — practise free

Instant marking, adaptive difficulty, and 14 spaced repetition flashcards. Free until your GCSEs.

Try PrepWise Free

Back to

Electrolysis of Molten Compounds

Electrolysis Cell — Click to Explore