BCECE Medical BCECE Medical Solved Papers-2003

  • question_answer
    Which of the following will have maximum pH?

    A)  \[\frac{M}{10}HCl\]

    B)  \[\frac{M}{100}HCl\]

    C)  \[\frac{M}{10}NaOH\]

    D)  \[\frac{M}{100}NaOH\]

    Correct Answer: C

    Solution :

    Key Idea: \[pH=-\log \,[{{H}^{+}}]\]                 \[pH=14-pOH\] Calculate pH of all the solution to find which will have maximum \[pH\]. [a] \[M/10\,HCl\] \[\therefore \,\,\,[{{H}^{+}}]={{10}^{-1}}\]                 \[pH=-\log \,\,[{{H}^{+}}]\]                 \[=-\log \,\,[{{10}^{-1}}]\]                 = 1 [b] \[M/100\,\,HCl\] \[\therefore \] \[[{{H}^{+}}]={{10}^{-2}}\]                 \[pH=-\log \,\,[{{H}^{+}}]\]                 \[=-\log \,\,[{{10}^{-2}}]\]                 = 2 [c] \[M/10\,\,NaOH\] \[\therefore \,\,\,[O{{H}^{-}}]={{10}^{-1}}\]                 \[pH=14-pOH\]                 \[=14\,\,[-\log \,{{10}^{-1}}]\]                 \[=14-1\]                 = 13 [d] \[M/100\,NaOH\] \[\therefore \] \[[O{{H}^{-}}]={{10}^{-2}}\]                 \[pH=14-pOH\]                 \[=14-[\log \,\,{{10}^{-2}}]\]                 \[=14-2=12\] \[\therefore \]  \[M/10\,\,NaOH\] solution has highest \[pH\].


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