JEE Chemistry 2025 Question with Solution

Given: Compound A shows a positive Lassaigne's test for $N$ and has molar mass $121$. Compound B gives effervescence with aqueous $\text{NaHCO}_3$. Compound C gives fruity smell. The scheme shows A converting to B with $\text{NaOH}$ followed by $\text{H}_3\text{O}^+$, and B converting to C with $\text{EtOH}$ and $\text{H}_2\text{SO}_4, \Delta$.

Find: Identify A, B, and C.

A positive Lassaigne's test for nitrogen shows that A contains nitrogen. From the solution working, the molar mass $121$ matches benzamide.

Treatment with base followed by acidic workup converts an amide into the corresponding carboxylic acid. Therefore,

So B is benzoic acid.

Effervescence with aqueous $\text{NaHCO}_3$ is characteristic of a carboxylic acid because $\text{CO}_2$ is evolved.

The next step uses $\text{EtOH}$ and $\text{H}_2\text{SO}_4$ with heating, which is esterification:

Esters give a fruity smell, so C is ethyl benzoate.

Therefore, A = benzamide, B = benzoic acid, C = ethyl benzoate. The correct option is A.

The solution indicates a discrepancy in the listed options: only the correct option content could be inferred from the solution, while the full option list was not available.

Given:

• A gives positive Lassaigne's test for $N$
• Molar mass of A is $121$
• B gives effervescence with aqueous $\text{NaHCO}_3$
• C gives fruity smell

Find: The identities of A, B, and C.

1. For A, the positive Lassaigne's test confirms the presence of nitrogen.
2. The solution text identifies the nitrogen-containing compound of molar mass $121$ as benzamide with formula $\text{C}_7\text{H}_7\text{NO}$.
3. Hydrolysis of an amide with $\text{NaOH}$ followed by acidification gives the corresponding carboxylic acid. Hence B is benzoic acid.
4. A compound that reacts with aqueous $\text{NaHCO}_3$ with effervescence must be a carboxylic acid, supporting that B is benzoic acid.
5. Reaction of a carboxylic acid with ethanol in presence of sulfuric acid and heat gives an ester. Thus C is ethyl benzoate.
6. Fruity smell is also a characteristic property of esters, confirming C.

Therefore, the identified set is benzamide, benzoic acid, ethyl benzoate, so the correct option is A.