Chemistry Gases SZABMU 2023
PMDC Verified Question 21 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 behavior assumes molecules have zero volume and zero intermolecular forces. Real gases violate these assumptions when molecules are forced close together or moving slowly.

Solution:

  • High Pressure: As pressure skyrockets, the gas is compressed. The empty space shrinks, meaning the actual physical volume of the gas molecules is no longer negligible compared to the total volume of the container.


  • Low Temperature: As temperature drops, the kinetic energy of the molecules plummets. They move slowly enough that their weak intermolecular attractive forces (van der Waals forces) take hold, pulling them together.


  • Therefore, the combination of low temperature and high pressure maximizes non-ideal behavior, eventually leading to the liquefaction of the gas.


Why other options are incorrect:

  • Option D: High temperature (fast moving) and low pressure (spaced far apart) is exactly when real gases behave most like ideal gases.
  • Options A & B: These offer conflicting conditions where one factor promotes ideality while 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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