The compounds that produce CO₂ with aqueous NaHCO₃ solution are:
Choose the correct answer from the options given below:

Solution

Chemistry ma’am · 3 steps

Bicarbonate gives off CO2 only with an acid stronger than carbonic acid, so compare every pKa with 6.4.

1. The test. An acid HA pushes HCO₃⁻ to H₂CO₃, which breaks into CO₂ + H₂O. This only happens if HA is a stronger acid than H₂CO₃, so its pKa must be below about 6.4.

   RCOOH + NaHCO₃ → RCOONa + H₂O + CO₂ ↑

   Compound	Approx. pKa	Stronger than H₂CO₃?	Gives CO₂?
   A: benzoic acid	4.2	yes	yes
   B: phenol	10.0	no	no
   C: picric acid (2,4,6-trinitrophenol)	0.4	yes, three -NO₂ groups stabilise the phenoxide	yes
   D: cyclohexanecarboxylic acid	4.9	yes, it is still a -COOH	yes
   E: 4-methoxyphenol	10.2	no, -OCH₃ donates electrons	no

2. Why C works. Three nitro groups at the ortho and para positions pull the negative charge of the phenoxide ion onto their oxygens by resonance. That makes picric acid stronger than most carboxylic acids.
3. So. A, C and D release CO₂ with aqueous NaHCO₃, which is option (d).

The idea to keep. The bicarbonate test sorts acids by strength, not by functional group. Every carboxylic acid passes, ordinary phenols fail, and a phenol with several strong electron-withdrawing groups such as picric acid passes.

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