Verified Solution • 2025–26 Session moderate

QJEEM19Ph1d56: JEE Main 2019 Physics - Class 11 JEEM19Ph1d56 Solution: A mixture of 2 moles of helium gas (atomic mass = 4 u), and 1…

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 (arg⁡on)],\left[ {{{{V_{rms}}\,(helium)} \over {{V_{rms}}\,(\arg on)}}} \right], is close to :

Multiple Choice Options

  • A 3.16
  • B 0.32
  • C 0.45
  • D 2.24

Step-by-Step Verified Solution

We know,

Vrms = 3RTM\sqrt {{{3RT} \over M}}

Where M = molar mass of the gas.

Here temperature is 300 K for both the gas. So temperature is constant. R is also a constant.

∴\therefore    Vrms ∝  1M\propto \,\,\sqrt {{1 \over M}}

∴\therefore     Vrms(helium∣)Vrms(arg⁡an))=MArMHe{{{V_{rms}}(helium|)} \over {{V_{rms}}\left( {\arg an)} \right)}} = \sqrt {{{{M_{Ar}}} \over {{M_{He}}}}}

= 404\sqrt {{{40} \over 4}}

= 10\sqrt {10}

= 3.16

Related Learning Resources & Exam Preparation

JEE Main PYQ Question Bank
Browse year-wise authentic previous years' questions with solutions
Authentic CBT Mock Tests
Simulate official exam environment with live timer and percentile scoring