See image — Practical Organic Chemistry and Purification Chemistry Question

💡 Solution & Explanation

Concept: To differentiate two compounds, we need a test that gives a positive result with one and a negative result with the other. Step 1 - Fehling test: Acetaldehyde (CH3CHO) is an aliphatic aldehyde and reduces Fehling's solution (alkaline copper(II) solution) to give a brick-red precipitate of Cu2O. Benzaldehyde (C6H5CHO) is an aromatic aldehyde and does NOT reduce Fehling's solution because the aromatic ring makes the carbonyl carbon less nucleophilic/reactive toward this reagent. Thus, Fehling's test can differentiate between them. Option (a) is valid. Step 2 - Iodoform test: Acetaldehyde has a CH3CO- group (methyl ketone/methyl aldehyde pattern) and gives a positive iodoform test, producing a yellow precipitate of CHI3. Benzaldehyde lacks a CH3CO- group and does NOT give a positive iodoform test. Thus, iodoform test can also differentiate between them. Option (b) is valid. Step 3 - Tollen's reagent: Both acetaldehyde and benzaldehyde give a positive Tollen's test (silver mirror test), as both are aldehydes capable of reducing ammoniacal silver nitrate. Tollen's reagent does NOT differentiate between them. Option (c) is invalid. Step 4 - Conclusion: Since both Fehling test and Iodoform test individually differentiate acetaldehyde from benzaldehyde, the correct answer is option (d) both (a) and (b). Therefore, the correct answer is D.