UPSC Prelims 2012 Q17: Environment & Ecology – Pollution & Waste Management
Consider the following statements: Chlorofluorocarbons, known as ozone - depleting
substances, are used
1. In the production of plastic foams
2. In the production of tubeless tyres
3. In cleaning certain electronic components
4. As pressurizing agents in aerosol cans
Which of the statements given above is/are correct?
- (a) 1, 2 and 3 only
- (b) 4 only
- (c) 1, 3 and 4 only
- (d) 1, 2, 3 and 4
Answer: (c) 1, 3 and 4 only
Explanation
Uses of chlorofluorocarbons (CFCs)
| Use | CFCs used? | Fact |
|---|---|---|
| 1. In the production of plastic foams | Yes | As blowing agents for foam |
| 2. In the production of tubeless tyres | No | Tyres are made of rubber compounds; no CFCs |
| 3. In cleaning certain electronic components | Yes | As solvents for circuit boards |
| 4. As pressurizing agents in aerosol cans | Yes | As propellants in sprays |
Other use: as refrigerants in refrigerators and air conditioners (Freon).
How CFCs harm the ozone layer:
| Step | What happens |
|---|---|
| Rise | CFCs drift up to the stratosphere |
| Break up | UV light frees chlorine atoms |
| Destroy | One chlorine atom destroys thousands of ozone molecules |
They are being phased out under the Montreal Protocol (1987).
Answer: (c) 1, 3 and 4 only.
Why each option is right or wrong
- (a) Incorrect. CFCs are not used in tubeless tyres, and aerosol cans are left out.
- (b) Incorrect. CFCs are also used in plastic foams and cleaning electronics.
- (c) CORRECT. CFCs are used in foams, electronics cleaning and aerosol cans.
- (d) Incorrect. Statement 2 on tubeless tyres is false.
Key point
CFCs: refrigerants, aerosol propellants, foam-blowing agents, solvents for electronics; release chlorine that destroys ozone; Montreal Protocol.
Remember
CFCs: fridge, aerosol, foam, solvent.
Common mistakes
- Adding tubeless tyres to the list.
- Forgetting the less obvious use as solvents for electronics.
- Thinking CFCs harm ozone in the troposphere; it happens in the stratosphere.
Exam tip
Four uses of CFCs: cool, spray, foam, clean.
Sources
- UN Environment Programme, Ozone Secretariat — The Montreal Protocol
- NCERT Class XI — Chemistry (Environmental Chemistry: ozone depletion)