Chlorofluorocarbons and the Ozone Layer

Question 1

What is the function of the ozone layer?

Answer 1

Protects living organisms from excessie UV radiation

Question 2

What is the equation for the formation of ozone?

Answer 2

• Oxygen molecule with UV to form 2 Oxygen radicals
• Oxygen molecule + Oxygen radical to reversible reaction to form Ozone molecule

Question 3

What causes CFCs to be stable?

Answer 3

The strength of the carbon-halogen bond meas they have a long residence time in the stratosphere.

Question 4

What type of fission does UV radiation use to break the C-X bond in CFCs?

Answer 4

homolytic fission

Question 5

Halogen radicals cause the [blank] of the ozone layer

fill in the blank

Answer 5

Catalysed breakdown

Question 6

Show the mechanism for the photodissociation of ozone (breaking down of ozone by halogen radicals)

Answer 6

Initiation- CF₂Cl₂ > CF₂Cl radical + Cl radical
Propagation step 1)Cl radical + Ozone > ClO radical + Oxygen molecule

Propagation step 2) ClO radical + Oxygen radical . Cl radical + Oxygen molecule

Overall equation- Ozone + Oxygen radical . 2 oxygen molecules

Question 7

What is the initiation step in the mechanism for the catalysed breakdown of ozone (photodissociation)

Answer 7

CF₂Cl₂ > CF₂Cl₂ radical + Cl radical

Question 8

Outline the propagation steps in the catalysed breakdown of ozone (photodissociation)

Answer 8

1) Chlorine radical + Ozone > ClO radical + Oxygen molecule
2) ClO radical + Oxygen radical > Chlorine radical + Oxygen molecule

Question 9

What is the overall equation for the photodissociation (catalysed break down by halogen radicals involving UV radiation) of ozone?

Answer 9

Ozone + Oxygen radical > 2 Oxygen molecules

Question 10

Show the mechanism for the breakdwon of ozone by Nitrogen Oxide radicals

Answer 10

Propagation step 1)NO radical + Ozone > NO₂ radical + Oxygen molecule

Propagation step 2) NO₂ radical + Oxygen radical . NO radical + Oxygen molecule

Overall equation- Ozone + Oxygen radical . 2 oxygen molecules

Question 11

What is the overall equation for the breakdown of ozone by Nitrogen oxide

Answer 11

Ozone + Oxygen radical > 2 Oxygen molecules