JEE Main & Advanced JEE Main Paper (Held on 09-4-2019 Morning)

  • question_answer Consider the van der Waals constants, a and b, for the following gases.
    \[\begin{matrix}    Gas & Ar & Ne & Kr & Xe  \\    a/(atm\,d{{m}^{6}}\,mo{{l}^{-2}}) & 1.3 & 0.2 & 5.1 & 4.1  \\    b/({{10}^{-2}}\,d{{m}^{3}}\,mo{{l}^{-1}}) & 3.2 & 1.7 & 1.0 & 5.0  \\ \end{matrix}\]
    Which gas is expected to have the highest critical temperature?             [JEE Main 9-4-2019 Morning]

    A) Kr        

    B) Ne

    C) Ar                               

    D) Xe

    Correct Answer: A

    Solution :

    \[{{T}_{c}}=\frac{8a}{27Rb}\] Greater value of\[\frac{a}{b}\Rightarrow \]higher is \['{{T}_{c}}'\] Gas a               \[{}^{a}/{}_{b}\] Ar                    \[\frac{1.3}{3.2}=0.406\] Ne                    \[\frac{0.2}{1.7}=0.118\] Kr                     \[\frac{5.1}{1}=5.1\] Xe                    \[\frac{4.1}{5}=0.82\] \[\therefore \]\[{{T}_{C}}\] has order : \[Kr>Xe>Ar>Ne\] \[\therefore \] Ans. is [a]                      


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