DUMET Medical DUMET Medical Solved Paper-2005

  • question_answer
    If equivalent conductance of 1M benzoic acid is \[12.8\,oh{{m}^{-1}}c{{m}^{2}}\] and if the conductance of benzoate ion and \[{{H}^{+}}\] ion are 42 and \[288.42\,oh{{m}^{-1}}c{{m}^{2}}\] respectively. Its degree of dissociation is :

    A)  39%          

    B)  3.9%

    C)  0.35%        

    D)  0.039%

    Correct Answer: B

    Solution :

    Key Idea: \[\alpha =\frac{\lambda }{{{\lambda }_{\infty }}}\] Given, \[f_{{{C}_{6}}{{H}_{5}}CO{{O}^{-}}}^{\infty }=42\,oh{{m}^{-1}}c{{m}^{2}}\] \[f_{{{H}^{+}}}^{\infty }=288.42\,oh{{m}^{-1}}c{{m}^{2}}\] \[{{\lambda }^{\infty }}_{{{C}_{6}}{{H}_{5}}COOH={{\lambda }^{\infty }}{{C}_{6}}{{H}_{5}}CO{{O}^{-}}+{{\lambda }^{\infty }}{{H}^{+}}}\] \[=42.0+288.42\] \[=330.42\,oh{{m}^{-1}}c{{m}^{2}}\] Given, \[{{\lambda }_{v}}=12.8\,oh{{m}^{-1}}c{{m}^{2}}\] \[\alpha =\frac{{{\lambda }_{v}}}{{{\lambda }_{\infty }}}=\frac{12.8}{330.42}\] \[=0.039\] \[=0.039\times 100\] \[=3.9%\]


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