Chemistry (5070)
Topic 6 of 8Cambridge O Levels

Electrochemistry

Electrolysis, electrodes, and industrial applications

Electrolysis = using electricity to decompose an ionic compound (electrolyte). The electrolyte must be molten or dissolved so ions can move.


Electrodes: **Anode** = positive electrode (oxidation: OIL). **Cathode** = negative electrode (reduction: RIG). Remember: **AN OX, RED CAT** (anode oxidation, reduction cathode).


At the cathode: Metal ions gain electrons → metal deposited. Cu²⁺ + 2e⁻ → Cu.

At the anode: Non-metal ions lose electrons → gas released. 2Cl⁻ → Cl₂ + 2e⁻.


Electroplating: Object = cathode, plating metal = anode, electrolyte contains metal ions. Example: silver-plating jewellery.


Industrial uses:

  • Extraction of aluminium from bauxite (molten cryolite + aluminium oxide)
  • Purification of copper — impure Cu anode, pure Cu deposits on cathode
  • Chlor-alkali industry — electrolysis of brine produces Cl₂, H₂, and NaOH

    • Key Points to Remember

    • 1Electrolysis needs molten or dissolved ionic compound
    • 2Anode = oxidation, Cathode = reduction (AN OX RED CAT)
    • 3Electroplating: object is cathode
    • 4Industrial: aluminium extraction, copper purification

    Pakistan Example

    Copper Wiring in Pakistan — Purified by Electrolysis

    Every electrical wire in Pakistani homes uses purified copper. Industrial electrolysis refines impure copper (99.5% pure anode) into ultra-pure copper (99.99% cathode) for electrical conductivity. Pakistan imports most refined copper — understanding the process helps evaluate industrial potential.

    Test Your Knowledge!

    3 questions to check if you understood this topic.

    Start Quiz
    Metals & ReactivityOrganic Chemistry