Exposure of chloroform to air in the presence of sunlight releases a gas which is poisonous. Identify the gas.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Phosgene
Chloroform is slowly oxidised by air in the presence of light to an extremely poisonous gas, carbonyl chloride (phosgene):
\( \ce{2CHCl3 + O2} \xrightarrow{\text{light}} \ce{2COCl2 + 2HCl} \)
For this reason chloroform is stored in closed, dark coloured bottles filled to the top, so that air is kept out.
NCERT (2026-27 edition):
Trichloromethane (Chloroform) – “… Chloroform is slowly oxidised by air in the presence of light to an extremely poisonous gas, carbonyl chloride, also known as phosgene.”