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JEE Main 2018 (15 Apr, Shift 2) · Molecular Speeds & Maxwell Distribution

Molecular Speeds & Maxwell Distribution question from JEE Main 2018 (15 Apr, Shift 2)

Q82JEE Main 2018 · 15 APR · SHIFT 2Easy

Molecular Speeds & Maxwell Distribution

The value closest to the thermal velocity of a Helium atom at room temperature (300 K) in ms-1 is: [kB =1.4 ×\times 10-23 J/K; mHe = 7 ×\times 10 -27 kg ]

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Answer: (b)

  1. Thermal (rms) speed v=3kBTmv = \sqrt{\frac{3k_BT}{m}}
  2. v=3×1.4×10−23×3007×10−27=1.8×106v = \sqrt{\frac{3 \times 1.4 \times 10^{-23} \times 300}{7 \times 10^{-27}}} = \sqrt{1.8 \times 10^{6}}
  3. v≈1.34×103 m/sv \approx 1.34 \times 10^{3}\text{ m/s}
  4. So the answer is (b) 1.3×103 m/s1.3 \times 10^{3}\text{ m/s}.
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