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BCECE Engineering BCECE Engineering Solved Paper-2012

  • question_answer
    Solution of \[\text{0}\text{.1 N N}{{\text{H}}_{\text{4}}}\text{OH}\]and \[\text{0}\text{.1 N N}{{\text{H}}_{\text{4}}}\text{Cl}\]has pH 9.25, then find out \[\text{p}{{\text{K}}_{b}}\]of \[\text{N}{{\text{H}}_{\text{4}}}\text{OH}\text{.}\]

    A)  9.25                      

    B)         4.75

    C)  3.75                      

    D)         8.25

    Correct Answer: B

    Solution :

    Solution of \[\text{N}{{\text{H}}_{\text{4}}}\text{OH}\] and \[\text{N}{{\text{H}}_{\text{4}}}\text{Cl}\]acts as a basic buffer solution. For basic buffer solution, \[pOH=p{{K}_{b}}+\log \frac{[Salt]}{[Base]}\] \[pOH=14-pH=14-9.25=4.75\] \[4.75=p{{K}_{b}}+\log \frac{0.1}{0.1}\] \[p{{K}_{b}}=4.75\]


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