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JEE Main & Advanced AIEEE Solved Paper-2012

  • question_answer
    The pH of a 0.1 molar solution of the acid HQ is 3. The value of the ionization constant, \[{{K}_{a}}\] of the acid is :   AIEEE  Solved  Paper-2012

    A) \[3\times {{10}^{-1}}\]                     

    B) \[1\times {{10}^{-3}}\]

    C) \[1\times {{10}^{-5}}\]                     

    D) \[1\times {{10}^{-7}}\]

    Correct Answer: C

    Solution :

                 \[HQ\,\,\,\,\overset{{}}{leftrightarrows}\,\,\,{{H}^{+}}+{{Q}^{-}}\]              \[0.1\]              \[0.1-x\]  \[x\]      \[x\]              \[pH=3,\,\,[{{H}^{+}}]={{10}^{-3}}\],          \[x={{10}^{-3}}\]              \[{{K}_{a}}=\frac{(x)\times (x)}{(0.1-x)}=\frac{{{({{10}^{-3}})}^{2}}}{0.1-{{10}^{-3}}}\simeq \frac{{{10}^{-6}}}{0.1}={{10}^{-5}}\]


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