See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Concept: NaHCO3 reacts only with strong acids (pKa < ~7), specifically carboxylic acids, to produce CO2 gas. NaOH reacts with both carboxylic acids and phenols (and other weak acids). A pair is 'differentiated by NaHCO3 as well as by NaOH' means both reagents can distinguish between the two compounds in the pair — i.e., one compound reacts with NaHCO3 and the other does not, AND one reacts with NaOH and the other does not (or they react differently with NaOH). Step 1: Analyze option (a) — Benzoic acid vs Phenol. - NaHCO3: Benzoic acid reacts (gives CO2), phenol does not. So NaHCO3 differentiates them. ✓ - NaOH: Both benzoic acid and phenol react with NaOH. So NaOH does NOT differentiate them (both dissolve/react). ✗ Option (a) fails because NaOH cannot differentiate them. Step 2: Analyze option (b) — Phenol vs Benzyl alcohol. - NaHCO3: Neither phenol nor benzyl alcohol reacts with NaHCO3 (phenol is too weak, pKa ~10; benzyl alcohol is even weaker). So NaHCO3 does NOT differentiate them. ✗ Option (b) fails. Step 3: Analyze option (c) — Benzoic acid vs Benzyl alcohol. - NaHCO3: Benzoic acid reacts with NaHCO3 (produces CO2), benzyl alcohol does not. NaHCO3 differentiates them. ✓ - NaOH: Benzoic acid reacts with NaOH (forms sodium benzoate), benzyl alcohol does not react with NaOH (it is a neutral alcohol, pKa ~15, too weak to react with NaOH under normal conditions). NaOH differentiates them. ✓ Option (c) satisfies both conditions. Step 4: Analyze option (d) — Phenol vs Anisole. - NaHCO3: Neither phenol nor anisole reacts with NaHCO3. So NaHCO3 does NOT differentiate them. ✗ Option (d) fails. Conclusion: Only option (c) — benzoic acid and benzyl alcohol — can be differentiated by BOTH NaHCO3 (benzoic acid reacts, benzyl alcohol does not) and NaOH (benzoic acid reacts, benzyl alcohol does not). Therefore, the correct answer is C.