KVPY Sample Paper KVPY Stream-SX Model Paper-28

  • question_answer
    1 mol of \[{{N}_{2}}\] at 0.8 atm takes 38 seconds to diffuse through a pin Hole, whereas 1 mol unknown compound of Xe with fluorine at 1.6 atm takes 57 seconds to diffuse through same hole. The molecular formula of the compound may be - \[[F=19]\,\,\,[Xe=131]\]

    A) \[Xe{{F}_{2}}\]

    B) \[Xe{{F}_{6}}\]

    C) \[Xe{{F}_{4}}\]

    D) None of these

    Correct Answer: B

    Solution :

    \[\frac{{{r}_{1}}}{{{r}_{2}}}=\frac{{{P}_{1}}}{{{P}_{2}}}\sqrt{\frac{{{M}_{2}}}{{{M}_{1}}}}\]
    \[\frac{\left( \frac{{{n}_{1}}}{{{t}_{1}}} \right)}{\left( \frac{{{n}_{2}}}{{{t}_{2}}} \right)}=\frac{{{P}_{1}}}{{{P}_{2}}}\sqrt{\frac{{{M}_{2}}}{{{M}_{1}}}}\,\,\,\,\left( r=\frac{n}{t} \right)\]
    \[\frac{\frac{1}{38}}{\left( \frac{1}{57} \right)}=\frac{0.8}{1.6}\sqrt{\frac{{{M}_{2}}}{28}}\]      \[\Rightarrow {{M}_{2}}=252\,\,gm\]
    so formula of compound is \[Xe{{F}_{6}}\]
    \[\because \,\,\,(131+6\times 19=245)\]


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