2017 H2 Chem P1 Q4 — Chemical bonding Solution

The answer is C (1 only).
Boiling a simple molecular substance overcomes the intermolecular forces between the molecules, so the boiling point reflects the strength of those forces.
• 1 is correct: water molecules are held together by strong hydrogen bonds, while methane molecules are held together only by weak instantaneous dipole-induced dipole (id-id) forces. Much more energy is needed to overcome the hydrogen bonds.
• 2 is incorrect: the covalent O-H and C-H bonds are within the molecules and are not broken on boiling, so their strength does not affect the boiling point.
• 3 is incorrect: \(\text{H}_2\text{O}\) and \(\text{CH}_4\) are isoelectronic. Each has exactly 10 electrons (O has 8 and 2 H give 2; C has 6 and 4 H give 4), so water does not contain more electrons than methane.
• A is wrong: it includes the incorrect statements 2 and 3.
• B is wrong: it includes the incorrect statement 2.
• D is wrong: it includes the incorrect statements 2 and 3 and leaves out the correct statement 1.