Compound(s) which will liberate carbon dioxide with sodium bicarbonate solution is/are :

Solution

Chemistry ma’am · 3 steps

Compare each compound with carbonic acid: anything stronger than it pushes CO₂ out of bicarbonate.

1. The test. RH + NaHCO₃ → RNa + H₂CO₃, and H₂CO₃ then breaks into H₂O + CO₂. This goes forward only if the compound is a stronger acid than H₂CO₃, whose pKₐ is about 6.4.

   Compound	Substituent effect	Approx. pKₐ	Stronger than H₂CO₃?
   A: 2,4,6-triaminophenol	three -NH₂ groups donate electrons (+R) and destabilise the phenoxide ion	above 10, weaker than phenol	No
   B: benzoic acid	carboxylate charge shared equally over two O atoms	4.2	Yes
   C: 2,4,6-trinitrophenol (picric acid)	three -NO₂ groups at ortho and para pull charge away (−R, −I) and stabilise the phenoxide ion	0.4	Yes

2. Why A fails. Plain phenol (pKₐ ≈ 10) is already too weak to react with NaHCO₃. Electron-donating amino groups make A even weaker, so no CO₂ is released.
3. So. Only B and C are stronger acids than carbonic acid, so both give brisk effervescence of CO₂. The answer is (c).

The idea to keep. The bicarbonate test is a strength contest with H₂CO₃ (pKₐ ≈ 6.4). Carboxylic acids and phenols carrying strong −R groups like several -NO₂ win; ordinary or electron-rich phenols lose.

Answer from the NTA final answer key. Solution by PrepWiser.