Chemistry Gases ETEA 2022
PMDC Verified Question 38 of 65
Which of the following shows marked deviation from ideal behaviour at a given temperature and pressure?
A
\( \text{CO}_2 \)
B
He
C
\( \text{N}_2 \)
D
\( \text{H}_2 \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \( \text{CO}_2 \)
Concept:

Deviation from ideal gas behavior is primarily driven by the presence of intermolecular forces (IMF) and the physical size (volume) of the gas molecules. Gases with larger molar masses and stronger IMFs deviate the most.

Solution:

  • Among the choices, Helium (He) and Hydrogen (\( \text{H}_2 \)) are extremely small molecules with very few electrons, resulting in very weak London dispersion forces. They behave almost ideally.


  • Nitrogen (\( \text{N}_2 \)) is larger but still non-polar and relatively small compared to carbon dioxide.


  • Carbon dioxide (\( \text{CO}_2 \)) is a much larger, multi-atomic molecule (44 g/mol) with a much larger electron cloud. This creates significantly stronger London dispersion forces.


  • Due to its larger size and stronger intermolecular attractions, \( \text{CO}_2 \) shows the most marked deviation from ideal behavior.


Why other options are incorrect:

  • Options B, C, & D: These gases have smaller atomic/molecular radii and significantly weaker intermolecular forces, keeping their behavior much closer to ideal.

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.

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