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JCECE Engineering JCECE Engineering Solved Paper-2012

  • question_answer
    The \[pH\] value of an acid is \[5\] and its concentration is\[1\,\,M\] . What is the value of \[{{K}_{a}}\] for the acid?

    A) \[{{10}^{-7}}\]                                  

    B) \[{{10}^{-5}}\]

    C) \[{{10}^{-10}}\]                                

    D) \[{{10}^{-8}}\]

    Correct Answer: C

    Solution :

    By using\[pH=-\log \sqrt{{{K}_{a}}}\cdot C\]                 \[5=-\log \sqrt{{{K}_{a}}\times 1}=-\frac{1}{2}\log {{K}_{a}}\]                 \[\log {{K}_{a}}=-10\]                         \[{{k}_{a}}={{10}^{-10}}\] Hence, dissociation constant\[({{K}_{a}})={{10}^{-10}}\]


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