Question

Chloroform, in the presence of air and sunlight, produces a poisonous gas known as:

• A. Phosgene
• B. Phosphine
• C. Tear gas
• D. Mustard gas

Hint:

To prevent the formation of toxic phosgene gas, chloroform is always stored in dark-coloured, tightly closed bottles filled to the brim.

Answer 1

The Correct Option is A

Step 1: Identify the reaction type.
Chloroform ($CHCl_3$) undergoes photo-oxidation, a slow reaction with atmospheric oxygen catalysed by sunlight (UV radiation).
Step 2: Write the chemical equation.
$2CHCl_3 + O_2 \xrightarrow{\text{sunlight}} 2COCl_2 + 2HCl$. The product $COCl_2$ is carbonyl chloride.
Step 3: Identify the product.
Carbonyl chloride ($COCl_2$) is historically and commonly known as phosgene. It is an extremely toxic gas used as a chemical warfare agent in World War I.
Step 4: Practical implication.
To prevent this hazardous transformation, chloroform is stored in dark amber bottles with a small amount of ethanol, which reacts with any phosgene formed to give the less harmful diethyl carbonate.
\[ \boxed{\text{Phosgene}} \]