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


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