Electrolysis

Science

Definition

Electrolysis is the process of using electrical energy to drive a non-spontaneous chemical reaction. An external power source forces electrons through an electrolyte solution, causing reduction at the cathode and oxidation at the anode.

How It Works

  1. An external power source (battery or DC supply) is connected to two electrodes immersed in an electrolyte.
  2. Cations migrate to the cathode (negative electrode) where they gain electrons (reduction).
  3. Anions migrate to the anode (positive electrode) where they lose electrons (oxidation).
  4. The non-spontaneous reaction proceeds as long as electrical energy is supplied.

Examples

  • Electrolysis of water (2H₂O → 2H₂ + O₂) produces hydrogen and oxygen gas
  • Electroplating uses electrolysis to coat objects with a thin layer of metal like gold or chrome
  • Aluminum is industrially extracted from bauxite ore using the Hall-Héroult electrolysis process
Key Fact

Electrolysis requires energy input (non-spontaneous, ΔG > 0); galvanic cells release energy (spontaneous, ΔG < 0).

Related Terms

Galvanic cells Ionic bonds Reaction types Gibbs free energy

Study This Concept

Practice electrolysis with free review games in these units:

AP Chemistry Unit 9: Applications of Thermodynamics