Chemistry - Aromatic Hydrocarbon Question with Solution | TestHub

Question Explanation : Count compounds that release ${\mathrm{CO}}_2$ with ${\mathrm{NaHCO}}_3$ (i.e., acids stronger than ${\mathrm{H}}_2{\mathrm{CO}}_3$ ).

Concept : Acidity Comparison ( ${\mathrm{pK}}_{\mathrm{a}}<6.4$ ).

Solution :

Reactive (Stronger Acids):

1. Methanesulphonic acid (CH₃SO₃H) : Strongest acid (pK_a ≈ –2).

2. Picric Acid: Very strong organic acid (pK_a ≈ 0.38).

3. 2,4-Dinitrophenol: Enhanced acidity ( pK_a≈ 4.0).

4. Benzoic Acid: Standard carboxylic acid ( pK_a≈ 4.2).

• Non-Reactive (Weaker Acids):    

• Phenol (pK_a≈ 10). and Ethanol (pK_a ≈ 16) are too weak.

• Total: 4 compounds

$NaHC{O}_3+$St. acid (more then H₂CO₃) → salt + H₂O +CO₂

Final Answer : 4