CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2006

  • 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                 \[R=0.0812\,L\]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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