AQA A Level Chemistry

Revision Notes

3.3.4 Ozone Depletion



  • The most common halogenoalkanes are chlorofluorocarbons (CFCs)
  • These compounds contain carbon atoms with chlorine and fluorine atoms attached to them
    • E.g. CCl3F and CCl2F2
  • CFCs have many uses due to their chemical inertness as they are non-flammable and non-toxic
    • They are used as refrigerators
    • Propellants for aerosols
    • As solvents for dry cleaning


  • Hydrofluorocarbons (HFCs) are compounds that contain a carbon attached to hydrogen and fluorine atoms only
    • Eg. CH2F-CF3
  • As with CFCs, HFCs are chemically inert and are therefore used for a wide range of purposes

Halogenoalkanes & The Ozone Layer

  • Though chlorofluorocarbons (CFCs) have many beneficial uses, they also have devastating effects on the ozone layer:
    • CFCs absorb a lot of UV radiation in the upper atmosphere
    • The CFCs are then broken down by the UV light causing the formation of chlorine radicals
    • These radicals react with ozone and break down the ozone layer
  • This is why hydrofluorocarbons (HFCs) are often used as an alternative to CFCs
  • As these compounds don’t contain any chlorine atoms, they will not have adverse effects on the ozone layer

Chlorine radicals and the ozone layer 


Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now
Already a member?
Go to Top