Answer the question on basis of passage given below:
The noble gases \(He\) to \(Rn\) have closed shell configuration and are monoatomic gases under normal conditions. Though mostly unreactive, direct reaction of Xe with \(F_2\) leads to a series of compounds with Xe oxidation numbers +2, +4 and +6. When certain compounds like phenol and quinol are crystallised in the presence of noble gas such as Ar, Kr and Xe a category of compound called clathrates are formed. In these the noble gas atoms are trapped in the cavities of the crystal lattices. The compounds which crystallise are known as hosts (H) while the noble gas atoms are called guests (G). The general formula of a clathrate compound is nHmG, where n is the number of host molecules and m is the number of guest atoms.
Which force is responsible for holding \(Ar\) in its clathrate compound with quinol?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → van der Waals
In a clathrate the noble gas atom is only trapped in a cavity of the host lattice (the passage says so). The quinol molecules are held to one another by hydrogen bonds and build the cage, but the Ar atom forms no chemical bond with them.
Argon has a closed-shell configuration, no charge and no permanent dipole. The only attraction between Ar and the walls of the cage is the weak van der Waals (dispersion) force, which arises from momentary dipoles. That is why Ar escapes as soon as the crystal is dissolved or melted.
Why the other options are incorrect
Option (2) Hydrogen bond — Incorrect. Hydrogen bonds hold the quinol molecules together in the host lattice; Ar has no H and no lone pair able to take part in one.
Option (3) Ionic bond — Incorrect. Needs transfer of electrons; argon forms no ion in a clathrate.
Option (4) Covalent bond — Incorrect. Argon shares no electrons with quinol; a clathrate is not a true chemical compound.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.