Question

Given below are two statements: Statement I: Griess–Ilosvay test is used for the detection of nitrite ion, which involves the use of sulphanilic acid and \(\alpha\)-naphthylamine reagent. Statement II: In the above test, sulphanilic acid is diazotized by the acidified nitrite ion, which on further coupling with \(\alpha\)-naphthylamine forms an azo-dye. In the light of the above statements, choose the correct answer from the options given below.

• A. Statement I is false but Statement II is true
• B. Both Statement I and Statement II are true
• C. Both Statement I and Statement II are false
• D. Statement I is true but Statement II is false

Hint:

Most nitrite detection tests involve diazotization reactions followed by azo-coupling, producing intensely colored dyes.

Answer 1

The Correct Option is B

Concept: The Griess–Ilosvay test is a classical qualitative test used in analytical chemistry for the detection of nitrite (\(\text{NO}_2^-\)) ions. It is based on diazotization followed by azo-coupling, resulting in the formation of a colored compound.
Step 1: Explanation of Statement I In the Griess–Ilosvay test:
Sulphanilic acid reacts with nitrite ions in acidic medium.
\(\alpha\)-naphthylamine is used as a coupling reagent. This confirms that the test indeed uses sulphanilic acid and \(\alpha\)-naphthylamine for the detection of nitrite ions. \[ \Rightarrow \text{Statement I is true.} \]
Step 2: Explanation of Statement II The reaction mechanism involves:
Nitrite ion in acidic medium produces nitrous acid.
Nitrous acid diazotizes sulphanilic acid to form a diazonium salt.
The diazonium compound couples with \(\alpha\)-naphthylamine to form a red or pink azo-dye. This is the characteristic observation of the Griess–Ilosvay test. \[ \Rightarrow \text{Statement II is also true.} \]
Step 3: Final conclusion Since both statements are correct and Statement II correctly explains Statement I: \[ \boxed{\text{Both Statement I and Statement II are true}} \]