BHU PMT BHU PMT (Mains) Solved Paper-2005

  • question_answer
    At STP the order of mean square velocity of molecules of\[{{H}_{2}},{{N}_{2}},{{O}_{2}}\]and\[HBr\]is:

    A)  \[{{H}_{2}}>{{N}_{2}}>{{O}_{2}}>HBr\]

    B)  \[HBr>{{O}_{2}}>{{N}_{2}}>{{H}_{2}}\]

    C) \[HBr>{{H}_{2}}>{{O}_{2}}>{{N}_{2}}\]

    D) \[{{N}_{2}}>{{O}_{2}}>{{H}_{2}}>HBr\]

    Correct Answer: A

    Solution :

                     Mean square velocity varies inversely with the square root of molar mass. \[{{u}_{rms}}\propto \frac{1}{\sqrt{molar\text{ }mass}}\] Molar mass of \[{{H}_{2}}=2,\text{ }{{N}_{2}}=14,\text{ }{{\text{O}}_{2}}=16,\text{ }HBr=81\]hence, \[{{u}_{rms}}\]velocity order is as . \[{{H}_{2}}>\text{ }{{N}_{2}}>{{O}_{2}}>HBr\]


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