JCECE Engineering JCECE Engineering Solved Paper-2003

  • question_answer
    The kinetic energy of \[1\,\,g\] molecule of a gas, at normal temperature and pressure is:\[(R=8.321\,\,J/mol\text{-}K)\]

    A) \[1.2\times {{10}^{2}}J\]                              

    B) \[3.4\times {{10}^{3}}J\]

    C)  \[1.66\times {{10}^{4}}J\]                           

    D)  \[2.97\times {{10}^{4}}J\]

    Correct Answer: B

    Solution :

    Key Idea: Average kinetic energy per molecule is equal to product of mass of \[1\,\,g\] molecule and square of mean square velocity. The kinetic energy of \[1\,\,g-\]mol is \[E=\frac{1}{2}M\,{{\bar{v}}^{2}}=\frac{1}{2}M\left( \frac{3RT}{M} \right)\]    \[\left[ \because \,\,\bar{v}=\sqrt{\frac{3RT}{M}} \right]\] where \[R\] is gas constant. Putting the numerical values, we have                 \[E=\frac{3}{2}\times 8.31\times 2.73=3.4\times {{10}^{3}}J\]


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