Match List-I with List-II.
| List-I (Compound) | List-II (Effect) |
|---|---|
| (A) Dichloromethane | (I) There is some evidence that exposure to it causes liver cancer in humans. |
| (B) Trichloromethane | (II) Exposure to lower levels of it in air can lead to slightly impaired hearing and vision. |
| (C) Tetrachloromethane | (III) It diffuses unchanged into the stratosphere, where it starts radical chain reactions that can upset the ozone balance. |
| (D) Freon 12 | (IV) Chronic exposure may damage the liver, where it is metabolised to phosgene. |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-II, B-IV, C-I, D-III
(A) Dichloromethane — This matches (II) Exposure to lower levels of it in air can lead to slightly impaired hearing and vision. Methylene chloride harms the central nervous system; higher levels cause dizziness, nausea and numbness in the fingers and toes.
(B) Trichloromethane — This matches (IV) Chronic exposure may damage the liver, where it is metabolised to phosgene. Chloroform is changed in the liver to phosgene, the same poisonous gas it forms with air in light; the kidneys can also be damaged.
(C) Tetrachloromethane — This matches (I) There is some evidence that exposure to it causes liver cancer in humans. Carbon tetrachloride can also make the heart beat irregularly. It too reaches the upper atmosphere and depletes the ozone layer.
(D) Freon 12 — This matches (III) It diffuses unchanged into the stratosphere, where it starts radical chain reactions that can upset the ozone balance. Freons are extremely stable, unreactive and non-toxic; their harm is to the ozone layer.
NCERT (2026-27 edition):
6.8.1 Dichloromethane (Methylene chloride) – “…Methylene chloride harms the human central nervous system. Exposure to lower levels of methylene chloride in air can lead to slightly impaired hearing and vision.”
6.8.2 Trichloromethane (Chloroform) – “…Chronic chloroform exposure may cause damage to the liver (where chloroform is metabolised to phosgene) and to the kidneys…”
6.8.4 Tetrachloromethane (Carbon tetrachloride) – “…There is some evidence that exposure to carbon tetrachloride causes liver cancer in humans.” … “When carbon tetrachloride is released into the air, it rises to the atmosphere and depletes the ozone layer.”
6.8.5 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. … Most freon, even that used in refrigeration, eventually makes its way into the atmosphere where it diffuses unchanged into the stratosphere. In stratosphere, freon is able to initiate radical chain reactions that can upset the natural ozone balance.”