Physics Thermodynamics PMDC Conceptual Practice
PMDC Verified Question 1 of 54
Two specific samples of ideal gases, marked '1' and '2', are contained at exactly the same temperature and pressure. If the ratio of their respective volumes is \( V_1:V_2 = 2:3 \), what is the ratio of their number of moles (\( n_1:n_2 \))?
A
\( \sqrt{2}:\sqrt{3} \)
B
\( 3:2 \)
C
\( 4:9 \)
D
\( 2:3 \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: \( 2:3 \)
Concept:

Avogadro's Law states that for ideal gases under identical conditions of temperature and pressure, volume is directly proportional to the number of moles.

Formula:

$$ V \propto n \implies \frac{V_1}{V_2} = \frac{n_1}{n_2} $$

Solution:

  • We are given identical T and P constraints.
  • The volume ratio \( V_1:V_2 \) is given directly as 2:3.
  • Because of direct linear proportionality, the ratio of moles \( n_1:n_2 \) must strictly follow the volume ratio.
  • Therefore, \( n_1:n_2 = 2:3 \).


Why other options are incorrect:

Option A assumes a square root relationship (typical of effusion rates). Option B incorrectly reverses the ratio. Option C assumes a squared relationship.

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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