The chlorofluorocarbon compounds of methane and ethane are collectively known as freons. Which of the following describes freons?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Extremely stable, unreactive, non-toxic, non-corrosive and easily liquefiable gases
Freons are the chlorofluorocarbon compounds of methane and ethane; freon 12, CCl2F2, is one of the most common. They are extremely stable, unreactive, non-toxic and non-corrosive gases that are easily liquefied, which is why they are produced for aerosol propellants, refrigeration and air conditioning.
Why the other options are incorrect
Option (1) Liquids widely used as paint removers and as metal cleaning and finishing solvents — Incorrect. This describes dichloromethane, a widely used solvent; freons are gases.
Option (2) Liquids that are slowly oxidised by air in the presence of light to a poisonous gas — Incorrect. This is chloroform, which is slowly oxidised by air in light to phosgene and so is stored in dark coloured bottles. Freons are unreactive.
Option (3) Fat soluble compounds that are not metabolised rapidly and are stored in the fatty tissues of animals — Incorrect. This describes the insecticide DDT, whose chemical stability and fat solubility let it build up in animals.
NCERT (2026-27 edition):
6.8.5 Freons – “The chlorofluorocarbon compounds of methane and ethane are collectively known as freons. They are extremely stable, unreactive, non-toxic, non-corrosive and easily liquefiable gases. Freon 12 (CCl2F2) is one of the most common freons in industrial use. … These are usually produced for aerosol propellants, refrigeration and air conditioning purposes.”