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JEE Main 2022 (28 Jul, Shift 2) · Molecular Speeds & Maxwell Distribution

Molecular Speeds & Maxwell Distribution question from JEE Main 2022 (28 Jul, Shift 2)

Q58JEE Main 2022 · 28 JUL · SHIFT 2Difficult

Molecular Speeds & Maxwell Distribution

A vessel contains 14 g14\text{ g} of nitrogen gas at a temperature of 27∘C27^\circ\text{C}. The amount of heat to be transferred to the gas to double the r.m.s speed of its molecules will be:

Take R=8.32 J mol−1 K−1R = 8.32\text{ J mol}^{-1}\text{ K}^{-1}.

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Answer: (c)

  1. n=1428=0.5n = \dfrac{14}{28} = 0.5 mol, T1=300T_1 = 300 K.
  2. vrms∝Tv_{rms} \propto \sqrt{T}: doubling vrmsv_{rms} needs T2=1200T_2 = 1200 K, ΔT=900\Delta T = 900 K.
  3. Heated in a closed vessel: Q=nCVΔTQ = nC_V\Delta T with CV=52R=20.8C_V = \dfrac{5}{2}R = 20.8 J mol−1^{-1}K−1^{-1}.
  4. Q=0.5×20.8×900=9360Q = 0.5 \times 20.8 \times 900 = 9360 J
  5. So the answer is (c) 9360 J.
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