C12: Electrolysis of Molten and Aqueous Ionic Compounds
Official Cambridge & Imperial ESAT specification requirements for Electrolysis of Molten and Aqueous Ionic Compounds on the Chemistry paper. Understand the syllabus boundaries, spot distractor traps engineered by examiners, and master the 2-step Sub-90 shortcuts that compress solve time well below the 88.8-second cutoff.
Official Syllabus Subtopics
Requirements specified in the UAT-UK framework
- 1Electrolyte definition and movement of ions under electric field
- 2Cathode (negative electrode, reduction: gain of e⁻) vs Anode (positive electrode, oxidation: loss of e⁻)
- 3Electrolysis of molten binary salts
- 4Aqueous discharge competition rules at cathode: metal discharged only if less reactive than hydrogen (Cu, Ag, Au)
- 5Aqueous discharge competition rules at anode: halide discharged if concentrated, otherwise O₂ from OH⁻
- 6Industrial extraction of aluminium via Hall-Héroult cell with molten cryolite solvent
Sub-90 Exam Speed Tips
How top candidates solve this spec under the 88.8s clock
At the cathode in aqueous solution, H₂ gas is evolved unless the metal is below hydrogen in reactivity (e.g. Cu).
At the anode in dilute solutions or solutions with sulfate/nitrate, OH⁻ is oxidised to produce O₂ gas: 4OH⁻ ⟶ O₂ + 2H₂O + 4e⁻.
Examiners engineer distractor options using common algebraic expansions and sign slips. Always test structural ratios or invariants before calculating arithmetic values.
Tested Topics in Specification C12
Master the individual question patterns and Sub-90 shortcuts for this specification.
Molten vs. Aqueous Electrolysis Discharge Competition & Electron Mole Stoichiometry
Aqueous discharge rules in 10s: Cathode (-) gives H2 unless metal is Cu, Ag, or Au. Anode (+) gives Halogen (Cl2, Br2, I2) if halide present, otherwise O2. For series cells, n(product) = n(e⁻) / (electrons per product in half-equation).
Ready to Master Specification C12 Under Exam Conditions?
Practice timed questions under the authentic Pearson VUE interface with live split stopwatch pacing, dry-wipe scratchpad, and distractor forensics.