JEE Main & Advanced AIEEE Solved Paper-2006

  • question_answer
    The molar conductivities \[\hat{\ }_{NaOAc}^{o}\]and \[\hat{\ }_{HCl}^{o}\]at infinite dilution in water at\[25{}^\circ C\]are 91.0 and \[426.2\text{ }S\text{ }c{{m}^{2}}/mol\]respectively. To calculate \[\hat{\ }_{HOAc'}^{o}\]the additional value required is     AIEEE  Solved  Paper-2006

    A) \[\hat{\ }_{{{H}_{2}}O}^{o}\]                     

    B)        \[\hat{\ }_{KCl}^{o}\]                    

    C)        \[\hat{\ }_{NaOH}^{o}\]              

    D)        \[\hat{\ }_{NaCl}^{o}\]

    Correct Answer: D

    Solution :

    At infinite dilution, when the dissociation of electrolyte is complete, each ion makes a definite contribution towards the total molar conductivity of electrolyte irrespective of the nature of the other ion with which it is associated. So use the Kohlrausch's law to solve the problem. According to Kohlrausch's law \[[NaOAc=C{{H}_{3}}\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-{{O}^{-}}N{{a}^{+}}]\] \[\lambda _{C{{H}_{3}}COOH}^{o}=\lambda _{C{{H}_{3}}CO{{O}^{-}}}^{o}+\lambda _{{{H}^{+}}}^{o}\]                  ??.(i) \[\lambda _{HCl}^{o}=\lambda _{{{H}^{+}}}^{o}+\lambda _{C{{l}^{-}}}^{o}\]                                      ??(ii) \[\lambda _{C{{H}_{3}}COONa}^{o}=\lambda _{C{{H}_{3}}CO{{O}^{-}}}^{o}+\lambda _{N{{a}^{+}}}^{o}\]                                ?(iii) Thus: on adding Eqs. (ii) and (iii) if\[\lambda _{N{{a}^{+}}}^{o}\]and\[\lambda _{C{{l}^{-}}}^{o}\] are subtracted we can obtained the value of\[\lambda _{HOAc}^{o}\]Thus, additional value required is\[\lambda _{NaCl}^{o}\].


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