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JEE Main 2021 (25 Jul, Shift 2) · Mean Free Path & Real Gases

Mean Free Path & Real Gases question from JEE Main 2021 (25 Jul, Shift 2)

Q15JEE Main 2021 · 25 JUL · SHIFT 2Medium

Mean Free Path & Real Gases

A system consists of two types of gas molecules A and B having same number density 2 ×\times 1025/m3. The diameter of A and B are 10 A˚\mathring{\text{A}} and 5 A˚\mathring{\text{A}} respectively. They suffer collision at room temperature. The ratio of average distance covered by the molecule A to that of B between two successive collision is ____________ ×\times 10−-2

Numerical answer type. Work it out, then open the answer.

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Answer: 25

  1. λ=12 nπd2\lambda = \dfrac{1}{\sqrt{2}\,n\pi d^2}; same nn, so λ∝1d2\lambda \propto \dfrac{1}{d^2}.
  2. λAλB=(dBdA)2=(510)2=0.25\dfrac{\lambda_A}{\lambda_B} = \left(\dfrac{d_B}{d_A}\right)^2 = \left(\dfrac{5}{10}\right)^2 = 0.25
  3. 0.25=25×10−20.25 = 25\times10^{-2}, so the answer is 25.
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