JEE Chemistry 2024 Question with Solution

Given: We must identify which of the listed compounds give a silver mirror with ammoniacal silver nitrate, that is, Tollens' reagent.

Find: The correct option(s).

Tollens' reagent is used to identify aldehydes. Aldehydes are oxidized to carboxylic acids, while silver ion is reduced to metallic silver, producing the silver mirror.

From the solution analysis:

1. Formic acid gives a positive Tollens' test because it is easily oxidized and can reduce the reagent.
2. Formaldehyde is an aldehyde, so it gives a positive Tollens' test.
3. Benzaldehyde is also an aldehyde, so it gives a positive Tollens' test.
4. Acetone is a ketone and does not give the silver mirror test.

Therefore, the compounds that give a silver mirror are A, B, and C only.

There is a discrepancy between the listed answer key and the extracted solution working. The solution clearly concludes that the correct answer is A, B, and C.

Given: The compounds are Formic acid, Formaldehyde, Benzaldehyde, and Acetone.

Find: Which of these respond positively to Tollens' reagent.

Tollens' test is a test for aldehydes, and formic acid is a known exception.

• Formic acid: Though a carboxylic acid, it behaves as a reducing agent and gives a silver mirror.
• Formaldehyde: Being an aldehyde, it is oxidized and gives a silver mirror.
• Benzaldehyde: As an aromatic aldehyde, it also gives a silver mirror.
• Acetone: Being a ketone, it does not respond to Tollens' reagent under normal conditions.

Hence, Formic acid, Formaldehyde, and Benzaldehyde give the test.

So the correct answer is A,B,C.