CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2008

  • question_answer
    For a concentrated solution of a weak electrolyte\[{{A}_{x}}{{B}_{y}}\]By of concentration C, the degree of dissociation\[\alpha \]is given as

    A) \[\alpha =\sqrt{{{K}_{eq}}/C(x+y)}\]

    B) \[\alpha =\sqrt{{{K}_{eq}}C/(xy)}\]

    C) \[\alpha ={{({{K}_{eq}}/{{C}^{x+y-1}}{{x}^{x}}{{y}^{y}})}^{1/(x+y)}}\]

    D) \[\alpha =({{K}_{eq}}/Cxy)\]

    E)  \[\alpha =({{K}_{eq}}/{{C}^{xy}})\]

    Correct Answer: C

    Solution :

    The weak electrolyte\[{{A}_{x}}{{B}_{y}}\]dissociates as follows \[{{A}_{x}}{{B}_{y}}\rightleftharpoons x{{A}^{y+}}+y{{B}^{x-}}\]             \[\begin{matrix}    C & \,\,\,\,\,\,\,\,0 & 0 & Initially  \\    C(1-\alpha ) & \,\,\,\,\,\,\,\,\,xC\alpha  & yC\alpha  & At\,equilibrium  \\ \end{matrix}\] where,  \[\alpha \]degree of dissociation \[C=\]concentration \[{{K}_{eq}}=\frac{{{[{{A}^{y+}}]}^{x}}{{[{{B}^{x-}}]}^{y}}}{[{{A}_{x}}{{B}_{y}}]}\]                 \[=\frac{{{[xC\alpha ]}^{x}}{{[yC\alpha ]}^{y}}}{C(1-\alpha )}\]                 \[=\frac{{{x}^{x}}.{{C}^{x}}.{{\alpha }^{x}}.{{y}^{y}}.{{C}^{y}}.{{\alpha }^{y}}}{C}\]            \[[\because 1-\alpha \approx 1]\]                 \[={{x}^{x}}.{{y}^{y}}.{{\alpha }^{x+y}}.{{C}^{x+y-1}}\] \[{{a}^{x+y}}=\frac{{{K}_{eq}}}{{{x}^{x}}.{{y}^{y}}.{{C}^{x+y-1}}}\]                 \[\alpha ={{\left( \frac{{{K}_{eq}}}{{{x}^{x}}.{{y}^{y}}.{{C}^{x+t-1}}} \right)}^{\left( \frac{1}{x+y} \right)}}\]


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