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WB JEE Medical WB JEE Medical Solved Paper-2013

  • question_answer
    At \[25{{\,}^{o}}C\]molar conductance of 0.1 molar aqueous   solution   of ammonium hydroxide is \[9.54\,oh{{m}^{-1}}\,c{{m}^{2}}\,mo{{l}^{-1}}\] and at infinite dilution its molar conductance is \[238\,oh{{m}^{-1}}\,c{{m}^{2}}mo{{l}^{-1}}.\] The degree of ionisation of ammonium hydroxide at the same concentration and temperature is

    A)  2.080%

    B)  20.800%

    C)  4.008%

    D)  40.800%

    Correct Answer: C

    Solution :

     Given, molar conductance at 0.1 M concentration, \[{{\lambda }_{c}}=9.54\,{{\Omega }^{-1}}\,c{{m}^{2}}\,mo{{l}^{-1}}\] Molar conductance at infinite dilution, \[\lambda _{c}^{\infty }=238\,{{\Omega }^{-1}}\,c{{m}^{2}}\,mo{{l}^{-1}}\] We know that, degree of ionisation, \[\alpha =\frac{{{\lambda }_{c}}}{\lambda _{c}^{\infty }}\times 100\] \[=\frac{9.54}{238}\times 100=4.008%\]


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