JIPMER Jipmer Medical Solved Paper-1999

  • question_answer
    One litre of a gas is at a pressure of \[{{10}^{-6}}\]mm of mercury at\[25{}^\circ C\]. How many molecules are present in the vessel?

    A)  \[3.2\times {{10}^{6}}\]

    B)                         \[3.2\times {{10}^{10}}\]            

    C)         \[3.2\times {{10}^{13}}\]            

    D)         \[3.2\times {{10}^{4}}\]

    Correct Answer: C

    Solution :

    According to question, \[{{P}_{1}}={{10}^{-6}}mm\,Hg\]              \[{{P}_{2}}=760\,mm\,Hg\] (S.T.P. conditions) \[{{T}_{1}}=298\,K\]        \[{{T}_{2}}=273\,K\] \[{{V}_{1}}=1\,\,litre\]   \[{{V}_{2}}=?\] From gas equation, \[\frac{{{P}_{1}}\,{{V}_{1}}}{{{T}_{1}}}=\frac{{{P}_{2}}\,{{V}_{2}}}{{{T}_{2}}}\] or \[{{V}_{2}}=\frac{{{10}^{-6}}\times 1\times 273}{760\times 298}=1.205\times {{10}^{-9}}\,\text{litre}\] Hence, number of molecules in \[1.205\times {{10}^{-9}}\] litre gas at S.T.P. \[=\frac{6.023\times {{10}^{23}}\times 1.205\times {{10}^{-9}}}{22.4}\] \[=3.24\times {{10}^{13}}\]


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