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NEET Sample Paper NEET Sample Test Paper-11

  • question_answer
    The rapid change of pH near the stoichiometric point of an acid-base titration is the basic of in dicator detection. pH of the solution is related to the ratio of the concentration of conjugate acid (HIn) and base\[(I{{n}^{-}})\]forms of the indicator by the expression

    A) \[\log \left[ \frac{I{{n}^{-}}}{HIn} \right]=p{{K}_{a}}+pH\]

    B) \[\log \left[ \frac{HIn}{I{{n}^{-}}} \right]={{K}_{a}}+pH\]

    C)  \[\log \left[ \frac{HIn}{I{{n}^{-}}} \right]=pH+p{{K}_{a}}\]

    D) \[\log \left[ \frac{I{{n}^{-}}}{HIn} \right]=pH-p{{K}_{a}}\]

    Correct Answer: D

    Solution :

     For \[HIn\rightleftharpoons {{H}^{+}}+I{{n}^{-}}\] \[{{K}_{a}}=\frac{[{{H}^{+}}][I{{n}^{-}}]}{[HIn]}\] \[\therefore \]\[pH=p{{K}_{a}}+\log \frac{[I{{n}^{-}}]}{[HIn]}\]


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