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JEE Main & Advanced JEE Main Paper (Held on 12-4-2019 Morning)

  • question_answer
    Two moles of helium gas is mixed with three moles of hydrogen molecules (taken to be rigid). What is the molar specific heat of mixture at constant volume? \[\left( R=8.3\text{ }J/mol\text{ }K \right)\]                                                                         [JEE Main Held on 12-4-2019 Morning]

    A) 21.6 J/mol K   

    B) 19.7 J/mol K

    C) 17.4 J/mol K   

    D) 15.7 J/mol K

    Correct Answer: C

    Solution :

    \[{{f}_{mix}}=\frac{{{n}_{1}}{{f}_{1}}+{{n}_{2}}{{f}_{2}}}{{{n}_{1}}+{{n}_{2}}}=\frac{2\times 3+3\times 5}{5}=\frac{21}{5}\]           \[{{C}_{\text{v}}}=\frac{fR}{2}=\frac{21}{5}\times \frac{R}{2}=17.4J/molK\]


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