JEE Main 2019PhysicsKinetic Theory of GasesEasyMCQ

JEE Main 2019Kinetic Theory of Gases Question with Solution

JEE Main 2019 (12 Apr Shift 2)

Question

The number density of molecules of a gas depends on their distance r from the origin as, nr=n0e-αr4. Then the numer of molecules is proportional to:

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Show full solutionCorrect option: C
Correct answer
Cn0α-34

Step-by-step explanation

Density of molecules of gas as a of r is, n(r)=n0e-αr4
Total no. of molecules =0n(r)dv
0n0e-αr44πr2dr
To integrate this, substitute u=α3/4r3  this will give us dr=13α3/4r2du
Now, the integration will become, 4πn03α3/4 0e-u4/3du
This shows that the numer of molecules is proportional to n0α-3/4

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About this question

This is a previous-year question from JEE Main 2019, covering the Kinetic Theory of Gases chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.