J & K CET Medical J & K - CET Medical Solved Paper-2010

  • question_answer
    What will be the resultant pH when 200 mL of an aqueous solution of\[HCl\]\[(pH=2.0)\]is mixed with 300 mL of an aqueous solution of\[NaOH\]\[(pH=12)\]?

    A)  2.699                                   

    B)  13.30

    C)  11.3010               

    D)  1.330

    Correct Answer: C

    Solution :

                     Given, volume of HCl solution = 200 mL pH of\[HCl\]solution =2.0 \[\therefore \]\[[{{H}^{+}}]\]in\[HCl\]solution\[=1\times {{10}^{-2}}\] \[\therefore \]Milliequivalents of\[HCl=200\times 1\times {{10}^{-2}}\]    \[=2\] Similarly, volume of\[NaOH\]solution = 300 mL pH of \[NaOH=12\] \[pOH\]of \[NaOH=14-12=2\] \[[O{{H}^{-}}]\]in\[NaOH\]solution\[=1\times {{10}^{-2}}\] \[\therefore \]Milliequivalents of\[NaOH\] \[=300\times 1\times {{10}^{-2}}=3\] Since,\[NaOH\]is in excess. \[\therefore \] Remaining milliequivalents \[=[O{{H}^{-}}]\] \[=3-2=1\] Remaining concentration of\[[O{{H}^{-}}]\] \[=\frac{1}{500}=2\times {{10}^{-3}}\] \[\therefore \]  \[[{{H}^{+}}]=\frac{{{10}^{-14}}}{2\times {{10}^{-3}}}\]                 \[=5\times {{10}^{-12}}\]                 \[pH=-\log [{{H}^{+}}]\]                 \[=-\log (5\times {{10}^{-12}})\] \[=11.3010\]


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