DUMET Medical DUMET Medical Solved Paper-2007

  • question_answer
    What will be the resultant pH when 200 mL of an aqueous solution of \[HCl\,(pH=2)\] is mixed with 300 mL of an aqueous solution of\[NaOH\,(pH=12)\]?

    A)  10            

    B)  11

    C)  12            

    D)  14

    Correct Answer: B

    Solution :

    Moles of \[{{H}^{+}}\] in 200 mL of \[{{10}^{-2}}MHCl=\frac{{{10}^{-2}}}{{{10}^{3}}}\times 200=2\times {{10}^{-3}}\] Moles of \[O{{H}^{-}}\] in 300 mL of \[{{10}^{-2}}MNaOH=\frac{{{10}^{-2}}}{{{10}^{3}}}\times 300=3\times {{10}^{-3}}\] Moles of \[O{{H}^{-}}\] left in 500 mL of solution \[=(3\times {{10}^{-3}})-(2\times {{10}^{-3}})\] \[=1\times {{10}^{-3}}\] No. of \[O{{H}^{-}}\] moles in \[1000\,mL=2\times {{10}^{-3}}\] \[[O{{H}^{-}}]=2\times {{10}^{-3}}M\] \[pOH=2.693\] \[pH=14-2.698=11.3020\approx 11\]


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