Manipal Medical Manipal Medical Solved Paper-2004

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


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