To determine which compound does NOT liberate CO₂ when treated with aqueous sodium bicarbonate (NaHCO₃), we need to understand the acidity of the compounds. Sodium bicarbonate is a weak base and reacts only with acids stronger than carbonic acid (H₂CO₃), liberating CO₂ gas. The reaction is:

$\mathrm{Acid}+\mathrm{NaHCO}{}_3\to \mathrm{Salt}+H_2\mathrm{CO}{}_3\to \mathrm{Salt}+H_{2}O+\mathrm{CO}{}_2\uparrow$

Carbonic acid decomposes to water and carbon dioxide. Therefore, only acids with a pK_a value less than that of carbonic acid (pK_a ≈ 6.3) will react with NaHCO₃ to produce CO₂. Acids with pK_a greater than 6.3 are weaker and will not liberate CO₂.

Now, let's analyze the given options:

• Benzenesulphonic acid: It is a strong acid (pK_a ~ -6.5), much stronger than carbonic acid. It will liberate CO₂.
• Benzoic acid: pK_a is about 4.2, which is less than 6.3. It will liberate CO₂.
• Carbolic acid (Phenol): pK_a is about 10, which is greater than 6.3. It is weaker than carbonic acid and will NOT liberate CO₂.
• Salicylic acid: pK_a is about 2.97 (due to intramolecular hydrogen bonding), which is less than 6.3. It will liberate CO₂.

Thus, Carbolic acid (Phenol) does NOT liberate CO₂ with aqueous NaHCO₃ because it is a weaker acid than carbonic acid.

Related Topics and Formulae

Acid Strength and pK_a: The lower the pK_a value, the stronger the acid. Sodium bicarbonate test is used to distinguish between strong acids (pK_a < 6.3) and weak acids (pK_a > 6.3).

Chemical Reaction: The general reaction for liberation of CO₂ is: $\mathrm{RCOOH}+\mathrm{NaHCO}{}_3\to \mathrm{RCOONa}+H_{2}O+\mathrm{CO}{}_2\uparrow$

Phenol's Acidity: Phenol is weakly acidic due to resonance stabilization of the phenoxide ion, but not enough to be stronger than carbonic acid.