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BHU PMT BHU PMT (Mains) Solved Paper-2010

  • question_answer
    What will be the pH of a solution formed by mixing 40 mL of\[0.10\text{ }M\text{ }HCl\]with 10 mL of\[0.45\text{ }M\text{ }NaOH\]?

    A)  12                                         

    B)  10

    C)   8                                           

    D)  6

    Correct Answer: A

    Solution :

                     Millimoles of\[HCl=40\times 0.10\text{ }M\] = 4 mmol Millimoles of\[NaOH=10\times 0.45\] =4.5 mmol Since,\[NaOH\]is in excess, millimoles of\[[O{{H}^{-}}]\]in mixture \[=(4.5-4)\text{ }mmol\] \[=0.5\text{ }mmol\] Concentration of\[O{{H}^{-}}\]in mixture\[=\frac{0.5}{40+10}\]                 \[=\frac{0.5}{50}=0.01\]                 \[pOH=-\log [O{{H}^{-}}]\]                 \[=-\log [1\times {{10}^{-2}}]\]                 \[=2\] \[pH+pOH=14\] \[pH=14-2=12\]


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