JEE Main & Advanced Chemistry Equilibrium Question Bank Electrical conductors, Arrhenius theory and ostwald's dilution law

  • question_answer If \[\alpha \] is the degree of ionization, \[C\] the concentration of a weak electrolyte and \[{{K}_{a}}\]the acid ionization constant, then the correct relationship between \[\alpha ,\,\,C\] and \[{{K}_{a}}\]is [CET Pune 1998; Pb. PMT 1998; RPMT 2002]

    A)                 \[{{\alpha }^{2}}=\sqrt{\frac{{{K}_{a}}}{C}}\]      

    B)                 \[{{\alpha }^{2}}=\sqrt{\frac{C}{{{K}_{a}}}}\]

    C)                 \[\alpha =\sqrt{\frac{{{K}_{a}}}{C}}\]     

    D)                 \[\alpha =\sqrt{\frac{C}{{{K}_{a}}}}\]

    Correct Answer: C

    Solution :

                    According to the Ostwald?s dilution formula \[{{\alpha }^{2}}=\frac{K(1-\alpha )}{C}\]. But for weak electrolytes a is very small. So that \[(1-\alpha )\] can be neglected. So that \[\alpha =\sqrt{\frac{{{K}_{a}}}{C}}\].

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