Question

Write the uses of freon. What is its impact on the environment?

Hint:

Freons are CFCs such as CCl₂F₂, used as refrigerants and propellants; in the stratosphere they release Cl radicals that deplete the ozone layer.

Answer 1

Step 1: What freons are. Freons are chlorofluorocarbons (CFCs), i.e. compounds of carbon containing both chlorine and fluorine. The most common is Freon-12, dichlorodifluoromethane, CCl₂F₂.
Step 2: Uses.
• As refrigerants in refrigerators and air conditioners.
• As propellants in aerosol sprays (perfumes, deodorants, insecticides).
• As blowing agents for making plastic foams and as cleaning solvents for electronic parts.
Step 3: Environmental impact. CFCs are very stable, so they slowly rise into the stratosphere. There, high-energy UV radiation breaks the C-Cl bond and produces chlorine free radicals:
\[CF_2Cl_2 \xrightarrow{UV} Cl^{\bullet} + CF_2Cl^{\bullet}\]
Step 4: Ozone destruction. The chlorine radical attacks ozone and destroys it in a chain (catalytic) manner:
\[Cl^{\bullet} + O_3 \rightarrow ClO^{\bullet} + O_2\]
\[ClO^{\bullet} + O \rightarrow Cl^{\bullet} + O_2\]
The Cl radical is regenerated, so one radical destroys thousands of ozone molecules, creating the ozone hole.
Step 5: Effect. Ozone depletion lets more harmful UV-B radiation reach the earth, causing skin cancer, cataracts, ageing of skin, and damage to plants and aquatic life.