Chemistry Gases UHS 2024
PMDC Verified Question 3 of 65
The real gases show deviation from ideal behaviour at:
A
Low temperature and low pressure
B
High temperature and high pressure
C
Low temperature and high pressure
D
High temperature and low pressure
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Low temperature and high pressure
Concept:

Ideal gas behavior is based on the assumption that gas molecules have negligible volume and zero intermolecular forces. Real gases deviate when these assumptions fail.

Solution:

  • At high pressure, gas molecules are forced close together. The empty space is minimized, making the actual physical volume of the gas molecules significant compared to the container's total volume.


  • At low temperature, the kinetic energy of the molecules drops. Because they are moving slower, their weak intermolecular attractive forces (van der Waals forces) have time to take effect, pulling them together.


  • Therefore, the combination of low temperature and high pressure causes the most significant deviation from ideal behavior, often leading to liquefaction.


Why other options are incorrect:

  • Option D: High temperature and low pressure are the exact conditions where real gases behave most ideally (fast-moving and far apart).
  • Options A & B: These provide conflicting conditions where one variable promotes ideality and the other promotes deviation.

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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