Concept:Surface tension arises from the net inward cohesive forces pulling on molecules at the surface of a liquid. Stronger cohesive forces result in higher surface tension.
Formula:$$ \gamma \propto \text{Cohesive Force Strength} $$
Solution:- Water and Ethyl alcohol rely on hydrogen bonding. Water has a high surface tension for a molecular liquid (approx 72 mN/m) due to its dense H-bond network.
- Chloroform relies on weaker dipole-dipole forces.
- Mercury (Hg), however, is a liquid metal. It is not held together by standard intermolecular forces, but by Metallic Bonding.
- The electrostatic sea of delocalized electrons creates an incredibly powerful cohesive force between the mercury atoms, resulting in a massive surface tension (approx 485 mN/m), pulling it tightly into spherical beads.
Why other options are incorrect:No molecular hydrogen bond (as in water or alcohol) can compete in strength with the pure metallic bonding found in liquid mercury.
Quality & Fidelity Assurance:
Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.