In the Griess-type test for nitrite, sulphanilic acid is treated with the test solution in acetic acid and then 1-naphthylamine is added to give a red dye. The species formed from sulphanilic acid before the addition of 1-naphthylamine is

Aa C-nitro compound
Ba diazonium salt
Can azo dye
Da hydrazine derivative

Answer: B

Nitrite with acetic acid gives

HNO X_{2}

, which diazotises the primary aromatic amine of sulphanilic acid to a diazonium salt. This diazonium ion then couples with 1-naphthylamine to give the red azo dye, so the azo dye is the final product, not the intermediate.

Practice Qualitative Analysis: Anions More on Dilute acid group anions: carbonate, sulphite, sulphide, nitrite

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