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JEE Main 2021 (27 Jul, Shift 1) · Pressure & Kinetic Energy of a Gas

Pressure & Kinetic Energy of a Gas question from JEE Main 2021 (27 Jul, Shift 1)

Q33JEE Main 2021 · 27 JUL · SHIFT 1Medium

Pressure & Kinetic Energy of a Gas

The number of molecules in one litre of an ideal gas at 300 K and 2 atmospheric pressure with mean kinetic energy 2 ×\times 10−-9 J per molecules is:

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Answer: (c)

  1. PV=23NEˉPV = \frac{2}{3}N\bar{E}, so N=3PV2EˉN = \frac{3PV}{2\bar{E}}.
  2. P=2P = 2 atm =2.026×105= 2.026 \times 10^{5} Pa, V=10−3V = 10^{-3} m3^3, Eˉ=2×10−9\bar{E} = 2 \times 10^{-9} J
  3. N=3×2.026×105×10−32×2×10−9≈1.5×1011N = \frac{3 \times 2.026 \times 10^{5} \times 10^{-3}}{2 \times 2 \times 10^{-9}} \approx 1.5 \times 10^{11}
  4. So the answer is (c) 1.5×10111.5 \times 10^{11}.
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