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JEE Main & Advanced JEE Main Paper (Held On 09-Jan-2019 Morning)

  • question_answer
    A Mixture of 2 moles of helium gas\[\left( atomic\text{ }mass=4u \right)\], and 1 mole of argon gas \[\left( atomic\text{ }mass=40u \right)\] is kept at 300 K in a container. The ratio of their rms speeds \[\left[ \frac{{{V}_{rms}}\,(helium)}{{{V}_{rms}}\,(argon\,)} \right]\] , is close to: [JEE Main Online Paper (Held On 09-Jan-2019 Morning]

    A) 0.32

    B) 3.16

    C) 2.24

    D) 0.45

    Correct Answer: B

    Solution :

    \[\because \,\,\,\,\,\,{{V}_{rms}}\,=\,\,\sqrt{\frac{3RT}{M}}\] for same temperature \[{{V}_{rms}}\,\propto \,\,\sqrt{\frac{1}{M}}\] \[\Rightarrow \,\,\,\,\,\,\frac{{{V}_{rms}}(He)}{{{V}_{rms}}\,(Ar)}\,\,=\,\,\sqrt{\frac{40}{4}}\,\,\,=\,\,\,\,\sqrt{10}\,\,=\,\,3.16\]


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