Benzenediazonium chloride is a colourless solid that decomposes in
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Dry state
Note: The given answer is as per the official NTA Answer Key. However, there is more than one correct option for this question, as explained below.
Benzenediazonium chloride is prepared by diazotisation of aniline with sodium nitrite and hydrochloric acid at 273–278 K:
\( \displaystyle \ce{C6H5NH2 + NaNO2 + 2HCl} \xrightarrow{273-278\ \text{K}} \ce{C6H5N2+Cl- + NaCl + 2H2O} \)
It is stable in cold aqueous solution, so it is made and used there. On warming with water it breaks down: the diazonium group is replaced by –OH and nitrogen is given off:
\( \displaystyle \ce{C6H5N2+Cl- + H2O} \xrightarrow{\text{warm}} \ce{C6H5OH + N2 + HCl} \)
The book uses the word “decomposes” for the dry state, so Option (1) is the answer given by NTA. But the book also says it reacts with water when warmed, losing nitrogen, so Option (3) warm water and Option (4), which names both conditions, are also correct.
Option (1) Dry state — Correct. The solid decomposes easily when dry, so it is never isolated but used in solution at once.
Option (2) Cold water — Incorrect. In cold aqueous solution the salt is stable; that is the very condition under which it is prepared and used.
Option (3) Warm water — Is also correct. The book says the salt is stable in cold water but reacts with water when warmed, giving phenol and nitrogen.
Option (4) Both dry state and warm water — Is also correct. It names both conditions in which the salt breaks down.
NCERT (2026-27 edition):
Physical Properties – …
