Concept:Physical properties of small organic molecules are dictated by their molecular weight and intermolecular forces.
Solution:- Formaldehyde (methanal) is a very small, lightweight molecule (Molar mass = 30 g/mol).
- Despite having a polar carbonyl bond, it lacks hydrogen bonding between its own molecules.
- Due to weak intermolecular forces, its boiling point is exceptionally low (-19°C).
- Therefore, it naturally exists as a pungent gas at room temperature. The statement that it is a liquid is NOT correct. (It is often dissolved in water to form a liquid solution called formalin, but the pure substance is a gas).
Why other options are incorrect:Statement A is true. Statement C is true (mild oxidation of methanol yields methanal). Statement D is true (calcium formate decomposes upon heating to yield formaldehyde and calcium carbonate).
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