Concept:Under identical conditions of temperature and pressure, the density of a gas is directly proportional to its molar mass.
Formula:$$ d = \frac{PM}{RT} \implies d \propto M \quad \text{(at constant P, T)} $$
Solution:- Let's calculate the molar masses of all the given gases:
- Neon (Ne) is a monoatomic noble gas: Molar mass = 20 g/mol.
- Nitrogen (\( \text{N}_2 \)) is diatomic: Molar mass = 14 × 2 = 28 g/mol.
- Oxygen (\( \text{O}_2 \)) is diatomic: Molar mass = 16 × 2 = 32 g/mol.
- Fluorine (\( \text{F}_2 \)) is diatomic: Molar mass = 19 × 2 = 38 g/mol.
- Since Neon has the lowest molar mass (20 g/mol), it will have the lowest density. The order of density is Ne < \( \text{N}_2 \) < \( \text{O}_2 \) < \( \text{F}_2 \).
Why other options are incorrect:- Options B, C, & D: Because they exist naturally as diatomic molecules, their molar masses are significantly heavier than monoatomic Neon, making them denser.
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.