Which of the following has the highest boiling point?

The correct answer is Option (4) → Tetrachloromethane

• The boiling point rises with the strength of the intermolecular forces. Van der Waals forces get stronger as a molecule gets bigger and has more electrons.

• Going from \( \ce{CH3Cl} \) to \( \ce{CH2Cl2} \), \( \ce{CHCl3} \) and \( \ce{CCl4} \), each step replaces an H atom by a much heavier Cl atom, so the molar mass rises: about 50.5, 85, 119.5 and 154 g mol⁻¹. \( \ce{CCl4} \) is the largest molecule with the most electrons, so it has the strongest van der Waals forces and the highest boiling point.

Why the other options are incorrect

Option (1) Chloromethane — Incorrect. With one Cl it is the smallest and lightest of the four; it is a gas at room temperature.

Option (2) Dichloromethane — Incorrect. With two Cl atoms its molecule is smaller and lighter than \( \ce{CHCl3} \) and \( \ce{CCl4} \), so its van der Waals forces are weaker.

Option (3) Trichloromethane — Incorrect. With one Cl atom fewer it is a smaller molecule with fewer electrons than \( \ce{CCl4} \), so its van der Waals forces are weaker and its boiling point is lower.

NCERT (2026-27 edition):
6.6 Physical Properties – “… Due to greater polarity as well as higher molecular mass as compared to the parent hydrocarbon, the intermolecular forces of attraction (dipole-dipole and van der Waals) are stronger in the halogen derivatives. … The attractions get stronger as the molecules get bigger in size and have more electrons.”