Which of the following compounds would release hydrogen when reacted with sodium metal?  I. CH$_3$COOH II. CH$_3$CH$_2$OH III. CH$_3$COOCH$_3$

Analyze the question: Sodium is a reactive metal. It releases hydrogen gas when it reacts with compounds that have an acidic hydrogen, meaning a hydrogen that can be replaced by the metal. In organic chemistry, these are the –OH groups in carboxylic acids and alcohols.

Concept:

• Carboxylic acids (–COOH) react with sodium to give a sodium salt and H₂.
• Alcohols (–OH) react with sodium more slowly to give a sodium alkoxide and H₂.
• Esters (–COO–R) have no hydrogen attached to oxygen, so they do not react with sodium to release hydrogen.

Step-by-step solution:

I. CH₃COOH (ethanoic acid) has an acidic –OH hydrogen: 2CH₃COOH + 2Na → 2CH₃COONa + H₂↑ It releases hydrogen.

II. CH₃CH₂OH (ethanol) has a hydroxyl group: 2CH₃CH₂OH + 2Na → 2CH₃CH₂ONa + H₂↑ It releases hydrogen (sodium ethoxide forms).

III. CH₃COOCH₃ (methyl ethanoate) is an ester. It has no –OH group and no replaceable hydrogen, so there is no reaction with sodium and no H₂.

Answer: Only I and II release hydrogen, so the correct option is B.

Tip: Remember "O–H releases H₂ with Na". If you see –OH (in an acid or an alcohol), sodium will liberate hydrogen. Esters, ethers, and alkanes will not.