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Which of the following gases is known as a tear gas?
A. Methyl isocyanide
B. Sulphur dioxide
C. Chloropicrin
D. Nitrous oxide

Last updated date: 20th Jun 2024
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Hint: Tear gas is a chemical weapon that irritates the mucous membrane of the eyes, causes a stinging sensation and tears. It also causes respiratory pain, skin irritation, bleeding and blindness. It is also known as a lachrymator agent or lachrymator (meaning tear).

Complete step by step answer:
Tear gas may cause severe effects to a person. It causes eye irritation, respiratory tract irritation and may even cause blindness.
It generally consists of aerosolized solid or liquid compounds. It causes coughing, pain in the eyes, difficulty in breathing, sneezing etc.
Now, from the above given options Chloropicrin is a powerful tear gas.
Its chemical formula is $C{l_3}CN{O_2}$ . It is a colorless liquid currently used as a broad spectrum antimicrobial, fungicide, herbicide and insecticide. It is manufactured by the reaction of nitromethane with sodium hypochlorite or by the reaction of chloroform with nitric acid. Both the reactions are as shown:
 ${H_3}CH{O_2} + 3NaOCl \to C{l_3}CN{O_2} + 3NaOH$
 $CHC{l_3} + HN{O_3} \to CC{l_3}N{O_2} + {H_2}O$
Moreover, in agriculture, chloropicrin is injected in the soil prior to planting a crop in order to fumigate soil. It affects a broad spectrum of fungi, microbes and insects.

Hence, option C is correct.

Note: Chloropicrin has a boiling point of ${112^ \circ }C$. Its vapors can cause severe irritation to skin and eyes. It is typically prepared by chlorination of either picric acid or nitromethane. It is also used as a chemical warfare agent and a riot control agent. It was used in large quantities during World War I and was stockpiled during World War II.