JEE Main & Advanced Sample Paper JEE Main - Mock Test - 15

  • question_answer
    The \[pH\] of \[{{10}^{-8}}M\] \[NaOH\] aqueous solution at \[25{}^\circ C\]is

    A) \[7.04\]    

    B)                    \[7.40\]    

    C) \[6.89\]                         

    D) \[6.0\]

    Correct Answer: A

    Solution :

    The neutral water has \[[O{{H}^{-}}]=1\times {{10}^{-7}}M\]
    By adding \[{{10}^{-8}}M\,\,NaOH,\] a concentration of \[{{10}^{-8}}M\,\,O{{H}^{-}}\] has increased in solution.
    Thus, total  \[[O{{H}^{-}}]={{10}^{-8}}+{{10}^{-7}}={{10}^{-8}}+10\times {{10}^{-8}}\]\[=11\times {{10}^{-8}}\]
    \[pOH=-\log 11\times {{10}^{-8}}=6.9586\]
    \[pH=14-6.9586=7.04\]


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