Manipal Engineering Manipal Engineering Solved Paper-2008

  • question_answer
    The density of a gas is\[1.964\,\,g\,\,d{{m}^{-3}}\]at\[273\,\,K\]and\[76\,\,cm\,\,Hg\]. The gas is

    A) \[C{{H}_{4}}\]

    B)                                        \[{{C}_{2}}{{H}_{6}}\]

    C) \[C{{O}_{2}}\]                   

    D)        \[Xe\]

    Correct Answer: C

    Solution :

    We know that,                 \[pV=nRT\] or            \[pV=\frac{w}{M}RT\] or            \[M=\frac{w}{V}\frac{RT}{p}\] or            \[M=d\frac{RT}{p}\]                 \[d=1.964\,\,g/d{{m}^{3}}=1.964\times {{10}^{-3}}\,\,g/cc\]                 \[p=76\,\,cm=1\,\,atm\]                 \[R=0.0821\,\,L\,\,atm\,\,{{K}^{-1}}mo{{l}^{-1}}\]                    \[=82.1\,\,cc\,\,atm\,\,{{K}^{-1}}mo{{l}^{-1}}\]               \[T=273\,\,K\]              \[M=\frac{1.964\times {{10}^{-3}}\times 82.1\times 273}{1}=44\] The molecular weight of\[C{{O}_{2}}\]is 44. So, the gas is\[C{{O}_{2}}\].


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