Uttarakhand PMT Uttarakhand PMT Solved Paper-2006

  • question_answer
    The pH of a\[{{10}^{-10}}M\,NaOH\]solution is:

    A)  10               

    B)  7.01

    C)  6.99             

    D)  4

    Correct Answer: A

    Solution :

     When the solution is very dilute, the concentration of\[O{{H}^{-}}\]produced from water cannot be neglected. Hence, \[[O{{H}^{-}}]={{10}^{-10}}+{{10}^{-7}}\] (obtained from water) \[=10-7(0.001+1)\] \[\therefore \] \[pOH=-log[O{{H}^{-}}]\] \[=-log(1.001\times {{10}^{-7}})\] \[=7-0.01=6.99\] \[\therefore \] \[pH=14-pOH\] \[=14-6.99=7.01\]


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