Knowledge Organiser: Electrolysis of Molten Compounds
Part of Electrolysis of Molten Compounds · GCSE GCSE Chemistry revision
This topic summary covers Knowledge Organiser: Electrolysis of Molten Compounds within Electrolysis of Molten Compounds for GCSE Chemistry. Revise Electrolysis of Molten Compounds in Electrolysis for GCSE Chemistry with 20 exam-style questions and 0 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 11 of 11 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 11 of 11
Practice
20 questions
Recall
0 flashcards
Knowledge Organiser: Electrolysis of Molten Compounds
Key Terms
- Cathode — negative electrode (reduction)
- Anode — positive electrode (oxidation)
- Cation — positive ion, moves to cathode
- Anion — negative ion, moves to anode
- Molten — melted; ions free to move
- Half equation — shows electron transfer at one electrode
Must-Know Facts
- Solid ionic compounds do NOT conduct electricity
- Molten compounds conduct — ions are free
- Cathode (−): cations gain electrons → METAL
- Anode (+): anions lose electrons → NON-METAL
- PbBr₂: Pb at cathode, Br₂ at anode
- NaCl: Na at cathode, Cl₂ at anode
- Ions carry current inside electrolyte (not electrons)
Key Equations
- Pb²⁺ + 2e⁻ → Pb (cathode — reduction of lead bromide)
- 2Br⁻ → Br₂ + 2e⁻ (anode — oxidation of lead bromide)
- Na⁺ + e⁻ → Na (cathode — reduction of sodium chloride)
- 2Cl⁻ → Cl₂ + 2e⁻ (anode — oxidation of sodium chloride)
Common Mistakes
- Saying solid ionic compounds conduct: Ions are fixed in the lattice when solid — only molten or dissolved ionic compounds allow ions to move and carry charge
- Getting electrode products reversed: OARC — Oxidation at Anode (non-metal), Reduction at Cathode (metal) — never swap these
- Saying electrons flow through the electrolyte: Electrons flow through the external circuit (wires); inside the electrolyte, ions carry the current by moving toward electrodes
- Forgetting to balance half-equations for charge: 2Br⁻ → Br₂ + 2e⁻ — the 2 electrons balance the 2 negative charges lost from bromide ions
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Practice Questions for Electrolysis of Molten Compounds
Which condition is required for electrolysis to occur with an ionic compound?
State the products formed at each electrode when molten lead bromide (PbBr₂) is electrolysed.
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