Ozone Depletion

What is the initiation stage of ozone depletion?

CCl3F --> CCl2F• + Cl•

How do CFCs deplete the ozone layer?

- CFCs diffuse into the stratosphere and undergo photolysis. - This is where they are broken down by light, creating chlorine free radicals. - These react with ozone to form an intermediate and oxygen.

What are CFCs?

- Chlorofluorocarbons. - They were widely used in industry as solvents and refrigerants.

How was action taken against ozone depletion?

- In the 1970s, research by several scientists demonstrated that CFCs were damaging the ozone layer so they were banned. - Chemists have developed safer alternatives such as hydrofluorocarbons (HFCs). - These have a lower toxicity and don't deplete the ozone layer as they do not contain chlorine.

What is the termination stage of ozone depletion?

2Cl• --> Cl2 (However, more commonly the Cl• reacts with the O3 again).

What is the overall equation for ozone depletion?

2O3 --> 3O2

What are the propagation stages of ozone depletion?

Cl• + O3 --> O2 + ClO• ClO• + O3 --> 2O2 +Cl• (This repeats as the Cl• is regenerated).

What is the purpose of ozone?

It enables the absorption of harmful UV rays, preventing a proportion of these harmful rays from reaching the surface of the Earth.

How is ozone formed?

It is formed from O2 and UV light.

What is the role of the chlorine free radicals?

They act as a catalyst as they are not used up, therefore contributing to a hole in the ozone layer.