JEE Main & Advanced Physics Kinetic Theory of Gases Question Bank Topic Test - Kinetic Theory of Gases

  • question_answer
    Let \[\overline{v},\,{{v}_{rms}}\] and \[{{v}_{p}}\] respectively denote the mean speed, root mean square speed and most probable speed of the molecules in an ideal monoatomic gas at absolute temperature T, the mass of a molecule is m. Then

    A) \[{{v}_{p}}<\overline{v}<{{v}_{rms}}\]

    B) The average kinetic energy of a molecule is \[\frac{3}{4}mv_{p}^{2}\]

    C) No molecule can have speed greater than \[\sqrt{2}{{v}_{rms}}\]

    D) No molecule can have speed less than \[{{v}_{p}}/\sqrt{2}\]

    Correct Answer: B

    Solution :

    [b]  \[{{v}_{rms}}=\sqrt{\frac{3RT}{M}},VP=\sqrt{\frac{2RT}{M}}=0.816\,{{v}_{rms}}\]
    \[\overset{\to }{\mathop{v}}\,=\sqrt{\frac{8RT}{\pi M}}=0.92\,{{v}_{rms}}\Rightarrow {{v}_{P}}<\overrightarrow{v}<{{v}_{rms}}\]
    Further \[{{E}_{av}}=\frac{1}{2}mv_{rms}^{2}=\frac{1}{2}m\frac{3}{2}v_{p}^{2}=\frac{3}{2}mv_{p}^{2}\]


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