JEE Main & Advanced Physics Kinetic Theory of Gases Sample Paper Topic Test - Kinetic Theory of Gases

  • question_answer
    A partition divides a container having insulated walls into two compartments I and II. The same gas fills the two compartments whose initial parameters are given. The partition is a conducting wall which can move freely without friction. Which of the following statement is correct, with reference to the final equilibrium position?

    A) The Pressure in the two compartments are unequal.

    B) Volume of compartment I is \[\frac{2V}{5}\]

    C) Volume of compartment II is\[\frac{12\,V}{5}\]

    D)  Final pressure in compartment I is \[\frac{4P}{3}\]

    Correct Answer: C

    Solution :

    [c] In the equilibrium position the net force on the partion will be zero.
    Hence pressure on both sides are same. Initially, PV = nRT
    \[{{n}_{1}}=\frac{{{P}_{1}}{{V}_{1}}}{R{{T}_{1}}}=\frac{PV}{RT}\]&
    \[\,{{n}_{2}}=\frac{\left( 2P \right)\left( 2V \right)}{RT}=4\frac{PV}{RT}\Rightarrow {{n}_{2}}=4{{n}_{1}}\]
    Moles remains conserved.
    Finally, pressure becomes equal in both parts.
    Using, \[{{P}_{1}}{{V}_{1}}=\text{ }{{n}_{1}}R{{T}_{1}}\]
    \[{{P}_{2}}{{V}_{2}}=\text{ }{{n}_{2}}R{{T}_{2}}\]
    \[\therefore \]    \[{{P}_{1}}={{P}_{2}}\And {{T}_{1}}={{T}_{2}}\]
    \[\therefore \]    \[\frac{{{V}_{1}}}{{{V}_{2}}}=\frac{{{n}_{1}}}{{{n}_{2}}}=\frac{1}{4}\,\,\,\,\Rightarrow \,\,\,{{V}_{2}}=4{{V}_{1}}\]
    Also     \[{{V}_{1}}+{{V}_{2}}=3V\]
    \[\Rightarrow \]            \[{{V}_{1}}+4{{V}_{1}}=3V\]
    And      \[{{V}_{2}}=\frac{12}{5}V\]
    In compartment (I):
    \[{{P}_{1}}'{{V}_{1}}=\text{ }{{n}_{1}}R{{T}_{1}}\]
    \[{{P}_{1}}\left( \frac{3V}{5} \right)=\left( \frac{PV}{RT} \right)RT\]
    \[{{P}_{1}}'=\frac{5PV}{3V}=\frac{5}{3}P\]


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