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

  • question_answer
    4.0 g of a gas occupies 22.4 liters at NTP. The specific heat capacity of the gas at constant volume is \[5.0J{{K}^{-1}}.\]If the speed of sound in this gas at NTP is \[952\text{ }m{{s}^{-1}},\] then the heat capacity at constant pressure is (Take gas constant \[R=8.3\text{ }J{{K}^{-1}}mo{{l}^{-1}}\])

    A) \[7.5\text{ }J{{K}^{-1}}mo{{l}^{-1}}\]

    B) \[7.0\text{ }J{{K}^{-1}}mo{{l}^{-1}}\]

    C) \[8.5J{{K}^{-1}}mo{{l}^{-1}}\]         

    D) \[8.0\text{ }J{{K}^{-1}}mo{{l}^{-1}}\]

    Correct Answer: D

    Solution :

    [d] Molar mass of the gas = 4g/mol Speed of sound \[V=\sqrt{\frac{\gamma RT}{m}}\Rightarrow 952=\sqrt{\frac{\gamma \times 3.3\times 273}{4\times {{10}^{-3}}}}\] \[\Rightarrow \,\,\,\,\,\,\,\,\,\gamma =1.6=\frac{16}{10}=\frac{8}{5}\] Also, \[\gamma =\frac{{{C}_{P}}}{{{C}_{v}}}=\frac{8}{5}\] \[\text{So, }{{C}_{p}}=\frac{8\times 5}{5}=8J{{K}^{-1}}mo{{l}^{-1}}\] \[\left[ {{C}_{v}}=\text{ }5.0\text{ }J{{K}^{-1}}given \right]\]


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