A school science club studied why some chemicals that were once common in household products have now been banned. Their teacher told them that these chemicals harm the ozone layer high above the Earth, and that countries have agreed together to stop their use.
Which of the following statements about such chemicals are correct?
(A) Chlorofluorocarbons (CFCs) are used as cooling substances in refrigerators and air-conditioners.
(B) Chlorofluorocarbons (CFCs) are used as aerosol propellants.
(C) Bromofluorocarbons (halons) are used in fire extinguishers.
(D) Halons are used as cooling substances in air-conditioners.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (B) and (C) only
CFCs and halons are the origins of the chlorine and bromine compounds that thin the ozone layer. Each has its own uses.
(A) Chlorofluorocarbons (CFCs) are used as cooling substances in refrigerators and air-conditioners. — Correct. This is a use of CFCs.
(B) Chlorofluorocarbons (CFCs) are used as aerosol propellants. — Correct. CFCs are also aerosol propellants.
(C) Bromofluorocarbons (halons) are used in fire extinguishers. — Correct. This is the use of halons.
(D) Halons are used as cooling substances in air-conditioners. — Incorrect. The cooling substances are CFCs; halons are used in fire extinguishers.
NCERT (2026-27): “Box 7.2: Ozone Depletion Ozone depletion refers to the phenomenon of reductions in the amount of ozone in the stratosphere. The problem of ozone depletion is caused by high levels of chlorine and bromine compounds in the stratosphere. The origins of these compounds are chlorofluorocarbons (CFC), used as cooling substances in air-conditioners and refrigerators, or as aerosol propellants, and bromofluorocarbons (halons), used in fire extinguishers. …” |