Physics Thermodynamics PMDC Conceptual Practice
PMDC Verified Question 3 of 54
In the kinetic theory of gases, the macroscopic pressure of an ideal gas is directly proportional to which specific molecular property?
A
Average vibrational kinetic energy of its molecules.
B
Total angular momentum of its molecules.
C
Average translational kinetic energy of its molecules.
D
The physical size of the molecules.
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Average translational kinetic energy of its molecules.
Concept:

Pressure is generated on container walls strictly by the linear momentum transfer of molecules impacting and bouncing off the walls.

Formula:

$$ P = \frac{2}{3} \left( \frac{N}{V} \right) \langle K.E._{\text{trans}} \rangle $$

Solution:

  • The equation states that Pressure (\( P \)) depends on the number density of the gas and the average kinetic energy of linear motion.
  • Linear motion corresponds to "translational" kinetic energy.
  • Therefore, pressure is directly proportional to the average translational kinetic energy.


Why other options are incorrect:

Vibrational and rotational kinetic energies contribute to the gas's internal heat capacity but do not contribute to momentum transfer (pressure) against the walls. Physical size is assumed to be zero in ideal gases.

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.

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.