Electrolysis (Edexcel GCSE Combined Science): Revision Note

Electrolysis

• When an electric current is passed through a molten or aqueous ionic compound the compound decomposes or breaks down

• Liquids and solutions that are able to conduct electricity are called electrolytes

• Covalent compounds cannot conduct electricity hence they do not undergo electrolysis

• An electrolytic cell is the name given to the set-up used in electrolysis and which consists of the following:

  • Electrode: a rod of metal or graphite through which an electric current flows into or out of an electrolyte

  • Electrolyte: ionic compound in molten or dissolved solution that conducts the electricity

  • Anode: the positive electrode of an electrolysis cell

  • Anion: negatively charged ion which is attracted to the anode

  • Cathode: the negative electrode of an electrolysis cell

  • Cation: positively charged ion which is attracted to the cathode

Diagram showing the direction of movement of electrons and ions in the electrolysis of NaCl

• During electrolysis the electrons move from the power supply towards the cathode

• Electron flow in electrochemistry thus occurs in alphabetical order as electrons flow from the anode to the cathode

• Positive ions within the electrolyte migrate towards the negatively charged electrode which is the cathode

• Negative ions within the electrolyte migrate towards the positively charged electrode which is the anode