Chemistry Gases MDCAT 2018
PMDC Verified Question 56 of 65
Gas is enclosed in a container of 20 \( \text{cm}^3 \) with the moving piston. According to kinetic theory of gases, what is the effect on freely moving molecules of the gas if temperature is increased from 20°C to 100°C?
A
Colliding capability of molecule will become lower
B
Pressure will become one half
C
Temperature has no effect on freely moving molecules
D
Volume will be increased
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Volume will be increased
Concept:

Charles's Law states that for a fixed mass of gas at constant pressure, the volume is directly proportional to its absolute temperature.

Solution:

  • A "moving piston" implies that the container is capable of expanding, maintaining a constant internal pressure equal to the external pressure.


  • When the temperature is increased from 20°C to 100°C, the average kinetic energy of the gas molecules increases.


  • They collide with the moving piston with greater force, pushing it outwards until the internal pressure equalizes with the external pressure.


  • As a result, the overall volume of the gas increases.


Why other options are incorrect:

  • Option A: Higher temperature increases kinetic energy, increasing the colliding capability (frequency and force) of the molecules.
  • Option B: The piston is movable, meaning pressure remains constant, it does not halve.
  • Option C: Temperature directly affects the kinetic energy and speed of freely moving molecules.

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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