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JEE Main 2019 (9 Jan, Shift 1) · Molecular Speeds & Maxwell Distribution

Molecular Speeds & Maxwell Distribution question from JEE Main 2019 (9 Jan, Shift 1)

Q75JEE Main 2019 · 9 JAN · SHIFT 1Easy

Molecular Speeds & Maxwell Distribution

A mixture of 2 moles of helium gas (atomic mass = 4 u), and 1 mole of argon gas (atomic mass = 40 u) is kept at 300 K in a container. The ratio of their rms speeds [Vrms(helium)Vrms(argon)],\left[\frac{V_{rms}(\text{helium})}{V_{rms}(\text{argon})}\right], is close to:

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Answer: (a)

  1. In a mixture both gases are at the same TT; the number of moles does not matter.
  2. vHevAr=MArMHe=404=10\frac{v_{He}}{v_{Ar}} = \sqrt{\frac{M_{Ar}}{M_{He}}} = \sqrt{\frac{40}{4}} = \sqrt{10}
  3. 10≈3.16\sqrt{10} \approx 3.16
  4. So the answer is (a) 3.16.
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