Depletion of the Ozone Layer

Question 1

What does ozone do in the stratosphere?

Answer 1

Absorb UV light from the Sun.

Question 2

How have views changed towards chlorofluorocarbons (CFCs) changed?

Answer 2

• Thought to be useful when they were first discovered in 1930s as they were inert
• Scientists now know that CFCs slowly move upwards to the stratosphere where they attack ozone
• Scientists agree that they deplete the ozone layer so they have been banned in the UK

Question 3

How does ozone absorb UV radiation?

Answer 3

• The UV waves are at the right frequency to make ozone molecules vibrate
• The energy of UV radiation is converted into KE inside of each molecule
• The thicker the ozone layer, the more UV radiation is absorbed

Question 4

How do CFCs deplete the ozone layer?

Answer 4

• The UV radiation from the Sun breaks up the CFCs to give highly reactive single chlorine atoms called chlorine radicals as the covalent bond splits into equal halves
• The chlorine radicals react with ozone molecules, turning the ozone back into oxygen and depleting the ozone layer
• UV light breaks down CFCs very slowly so they stay in the stratosphere for a very long time

Question 5

What does each chlorine radical set off?

Answer 5

A chain reaction.

Question 6

What are the stages of ozone depletion in terms of equations?

Answer 6

• Cl* + O3 —> OCl* + O2
• OCl* + O3 —> Cl* + 2O2
• Combining the two gives 2O3 —> 3O2
• Eventually Cl* + Cl* —> Cl2