Match List-I with List-II.
| List-I (Reactants) | List-II (Observation) |
|---|---|
| (A) Ethanoic acid and sodium metal | (I) No reaction takes place. |
| (B) Ethanoic acid and sodium hydrogencarbonate solution | (II) Hydrogen gas is evolved. |
| (C) Phenol and sodium hydrogencarbonate solution | (III) A salt and water are formed, with no gas evolved. |
| (D) Phenol and aqueous sodium hydroxide | (IV) Carbon dioxide gas is evolved. |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-II, B-IV, C-I, D-III
Carboxylic acids and phenols are both acidic, but carboxylic acids are much stronger acids. Both react with an active metal and with an alkali; only the carboxylic acid is strong enough to react with a weak base such as sodium hydrogencarbonate.
(A) Ethanoic acid and sodium metal — This matches (II) Hydrogen gas is evolved. Sodium is an electropositive metal:
\( \displaystyle \ce{2CH3COOH + 2Na -> 2CH3COONa + H2 ^} \)
(B) Ethanoic acid and sodium hydrogencarbonate solution — This matches (IV) Carbon dioxide gas is evolved. The brisk effervescence is used to detect a carboxyl group:
\( \displaystyle \ce{CH3COOH + NaHCO3 -> CH3COONa + H2O + CO2 ^} \)
(C) Phenol and sodium hydrogencarbonate solution — This matches (I) No reaction takes place. Phenol is too weak an acid to react with a hydrogencarbonate, so no carbon dioxide is given off.
(D) Phenol and aqueous sodium hydroxide — This matches (III) A salt and water are formed, with no gas evolved. With a strong base, phenol forms sodium phenoxide:
\( \displaystyle \ce{C6H5OH + NaOH -> C6H5ONa + H2O} \)
NCERT (2026-27 edition):
8.9.1 Reactions Involving Cleavage of O–H Bond – “The carboxylic acids like alcohols evolve hydrogen with electropositive metals and form salts with alkalies similar to phenols. However, unlike phenols they react with weaker bases such as carbonates and hydrogencarbonates to evolve carbon dioxide. This reaction is used to detect the presence of carboxyl group in an organic compound.”
7.4.4 Chemical Reactions – “In addition to this, phenols react with aqueous sodium hydroxide to form sodium phenoxides.”