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JEE Main & Advanced JEE Main Solved Paper-2017

  • question_answer
    \[\text{p}{{\text{K}}_{\text{a}}}\]of a weak acid (HA) and \[\text{p}{{\text{K}}_{\text{b}}}\]of a weak base (BOH) are 3.2 and 3.4, respectively. The pH of their salt (AB) solution is     JEE Main Solved Paper-2017

    A)  7.2                                        

    B)  6.9

    C)  7.0                                        

    D)  1.0

    Correct Answer: B

    Solution :

     Given \[p{{K}_{a}}(HA)=3.2\] \[p{{K}_{b}}(BOH)=3.4\] As given salt is of weak acid and weak bas \[\therefore \]  \[pH=7+\frac{1}{2}p{{K}_{a}}-\frac{1}{2}p{{K}_{b}}\] \[=7+\frac{1}{2}(3.2)-\frac{1}{2}(3.4)\]                 \[=6.9\]


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