JEE Advanced Chemistry: Organic Chemistry — General Principles questions with solutions

Q1. How many of the following compounds liberate CO2 gas on reaction with aqueous NaHCO3? (a) Oxalic acid (HOOC-COOH) (b) Benzoic acid (C6H5COOH) (c) Benzene-1,4-diol (hydroquinone) (d) Toluene (C6H5CH3) (e) Phenylacetylene (C6H5-C≡CH) (f) Sulfuric acid (H2SO4) (g) Acetic acid (CH3COOH)

1. 0
2. 1
3. 2
4. 3

Answer: 3

A compound liberates CO2 from NaHCO3 only if it is a stronger acid than H2CO3 (pKa1 = 6.35). Among the listed compounds, oxalic acid (pKa1 = 1.25), benzoic acid (pKa = 4.20), and acetic acid (pKa = 4.76) satisfy this criterion. H2SO4 is a strong acid but is typically counted separately; benzene-1,4-diol (pKa ~9.9), toluene, and phenylacetylene (pKa ~25) are too weak.