What is the name of the diazonium salt C6H5N2+HSO4−?

The correct answer is Option (2) → Benzenediazonium hydrogensulphate

• A diazonium salt is named by adding diazonium to the name of the parent hydrocarbon (here benzene, not aniline, the amine from which the salt is made) and then naming the anion.

• The anion \( \ce{HSO4-} \) is hydrogensulphate (\( \ce{SO4^2-} \) is sulphate and \( \ce{HSO3-} \) is hydrogensulphite).

• So \( \ce{C6H5N2^+HSO4^-} \) is benzenediazonium hydrogensulphate, just as \( \ce{C6H5N2^+Cl^-} \) is benzenediazonium chloride.

NCERT (2026-27 edition):
II. Diazonium Salts – “They are named by suffixing diazonium to the name of the parent hydrocarbon from which they are formed, followed by the name of anion such as chloride, hydrogensulphate, etc. The N₂⁺ group is called diazonium group. For example, C₆H₅N₂⁺Cl^– is named as benzenediazonium chloride and C₆H₅N₂⁺HSO₄^– is known as benzenediazonium hydrogensulphate.”