Cambridge IGCSE Chemistry · Syllabus 0620 · Electrochemistry
Electrolysis
What is Electrolysis?
The decomposition of an ionic compound, either molten or in aqueous solution, brought about by passing an electric current through it. The compound must be ionic, it must be molten or dissolved in water so that its ions are free to move, and a current must be passed through it; the elements of the compound are then released at the two electrodes.
This definition is part of the Electrochemistry chapter in Cambridge IGCSE Chemistry.
Electrolysis in context
Electrolysis is the decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current. Everything else in this chapter follows from one question asked in order: what is in the liquid, which electrode does each part reach, what is released there, and what would you see? Read this map in seven to ten minutes before the lessons, and again the night before the paper.
Common mistakes with Electrolysis
- Aluminium extraction, bauxite, cryolite and carbon-anode consumption. These are examined — but in Topic 9, not here. Statement 9.6 makes bauxite and extraction by electrolysis a Core requirement, and adds cryolite, anode replacement and the electrode half-equations at Supplement. Revise them with the metals chapter; do not bring them into a Topic 4 answer.
- 5. "Molten and aqueous electrolysis work the same way." Core 4.1.3 Repair A molten compound supplies only its own two ions, but an aqueous solution has water present as well, so the solution, its concentration and the electrode material can all change the answer. Taught in Lesson C.