RAJASTHAN PMT Rajasthan - PMT Solved Paper-2008

  • question_answer
    \[A\,\,0.1\] aqueous solution of a weak acid is\[2%\] ionized. If the ionic product of water is \[1\times {{10}^{-4}},\] the \[[O{{H}^{-}}]\] is

    A) \[5\times {{10}^{-12}}M\]                           

    B)        \[2\times {{10}^{-3}}M\]

    C)        \[1\times {{10}^{-4}}M\]                             

    D)         None of these

    Correct Answer: A

    Solution :

    Since, it is a weak acid, the equation to calculate \[[{{H}^{+}}]\] is                 \[=C\times \alpha (\alpha =%\]of ionization)                 \[=0.1\times 0.02=2\times {{10}^{-3}}M\]         \[{{K}_{w}}=[{{H}^{+}}][O{{H}^{-}}]\]   \[[O{{H}^{-}}]=\frac{{{K}_{w}}}{[{{H}^{+}}]}=\frac{1\times {{10}^{-14}}}{2\times {{10}^{-3}}}\]                 \[=5\times {{10}^{-12}}M\]


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