stpm 1 (Free Radical Reaction)

2.
Each chlorine atom that is produced from chlorofluoroalkane in the stratosphere can destroy almost a hundred thousand ozone molecules. Explain. [5]

Answer:

Chorofluoroclkanes, such as Freon can initiate a free radical chain reaction.

Initiation step: CF2Cl2 + light (UV) ---> CF2Cl● + Cl●

Propagation step: Cl● + O3 --> ClO● + O2
ClO● + O3 --> Cl● + 2O2

In the propagation step, ozone is destroyed and the chlorine radical Cl● is regenerated. Therefore, one chlorine atom ( in the form of a radical) can destroy thousands of ozone molecules. The chlorine radical can only be annihilated by colliding with another chlorine radical.

Cl● + Cl● -> Cl2