CET Karnataka Medical CET - Karnataka Medical Solved Paper-2009

  • question_answer
    \[{{10}^{-6}}M\text{ }NaOH\]is diluted 100 times. The pH of the diluted base is

    A)  Between 7 and 8

    B)  Between 5 and 6                        

    C)  Between 6 and 7

    D)  Between 10 and 11

    Correct Answer: A

    Solution :

    \[[O{{H}^{-}}]\] in the diluted base \[=\frac{{{10}^{-6}}}{{{10}^{2}}}={{10}^{-8}}\] Total \[[O{{H}^{-}}]={{10}^{-8}}+[O{{H}^{-}}]\]of water \[=({{10}^{-8}}+{{10}^{-7}})M\] \[={{10}^{-8}}[1+10]M\] \[=11\times {{10}^{-8}}M\] \[pOH=-\log 11\times {{10}^{-8}}\] \[=-\log 11+8\log 10\] \[=6.9586\] \[pH=14-6.9586\] \[=7.0414\]


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