Electrolytes

Specification Point 3.22:
  • Recall that electrolytes are ionic compounds in the molten state or dissolved in water.
  • Molten ionic compounds are able to conduct electricity in a process called electrolysis.
  • The process also occurs for aqueous solutions of ionic compounds.
  • Electrolyte is the term used to describe the ionic compound (molten or aqueous solution) that conducts the electricity.
  • In electrolytes the ions are free to move around within the liquid or solution and thus can carry charge, which is how electrolytes conduct electricity.
  • Ionic compounds in the solid state cannot conduct electricity either since they have no free ions, they are all in fixed positions in the ionic lattice structure.

Ionic Solid and Molten, Edexcel GCSE Chemistry

Particles in ionic compounds are in fixed position in the solid state but can move around when molten or in solution

Electrolysis

Specification Point 3.23:
  • Describe electrolysis as a process in which electrical energy, from a direct current supply, decomposes electrolytes.

Electrolysis

  • When an electric current is passed through an electrolyte it decomposes or breaks down.
  • The current separates the elements that form the electrolyte.
  • Electrolysis can therefore be described as a process that uses direct electricity to decompose electrolytes.

Key Terms

  • Electrode is a rod of metal or graphite through which an electric current flows into or out of an electrolyte.
  • Electrolyte is the ionic compound in molten or dissolved solution that conducts the electricity.
  • Anode is the positive electrode of an electrolysis cell.
  • Anion is a negatively charged ion which is attracted to the anode.
  • Cathode is the negative electrode of an electrolysis cell.
  • Cation is a positively charged ion which is attracted to the cathode.

Basic Electrolysis Setup, Edexcel GCSE Chemistry

The basic set-up of an electrolysis cell

Movement of Ions

Specification Point 3.24:
  • Explain the movement of ions during electrolysis, in which:
    a) positively charged cations migrate to the negatively charged cathode
    b) negatively charged anions migrate to the positively charged anode
  • 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.

Transfer of Charge, Edexcel GCSE Chemistry

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

Edexcel GCSE Chemistry Notes

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.