BVP Medical BVP Medical Solved Paper-2013

  • question_answer
    The pH of a \[1.0\times {{10}^{-8}}M\] solution of \[HCl\] is

    A)  \[6\]                                    

    B)  \[7\]

    C)  \[8\]                                    

    D)  \[6.98\]

    Correct Answer: D

    Solution :

                    \[HCl(aq)+{{H}_{2}}O(l){{H}_{3}}{{O}^{+}}(aq)+C{{l}^{-}}(aq)\] \[2{{H}_{2}}O(l){{H}_{3}}{{O}^{+}}(aq)+O{{H}^{-}}(aq)\] Sources of \[{{H}_{3}}{{O}^{+}}\] ions are both \[HCl\] and \[{{H}_{2}}O\]. Hence,        \[[{{H}_{3}}{{O}^{+}}]={{10}^{-6}}+x\] \[\because \]     \[{{K}_{w}}={{10}^{-14}}\] \[\therefore \]  \[{{10}^{-14}}=[{{10}^{-8}}+x][x]\] or            \[{{x}^{2}}+{{10}^{-8}}x-{{10}^{-14}}=0\] or            \[x=9.5\times {{10}^{-8}}\] or            \[x=[O{{H}^{-}}]9.5\times {{10}^{-8}}\] \[\therefore \]  \[pOH=7.02\]and \[pH=6.98\]


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