JEE Main & Advanced Chemistry Equilibrium / साम्यावस्था Question Bank Hydrogenion concentration pH scale and buffer solution

  • question_answer
    What will be the \[pH\]of a \[{{10}^{-8}}\,M\,HCl\] solution [MP PET/PMT 1998; RPET 1999;MP PMT 2000]

    A)                 8.0         

    B)                 7.0

    C)                 6.98       

    D)                 14.0

    Correct Answer: C

    Solution :

               \[{{H}_{2}}O\]⇌\[[{{H}^{+}}]\,\,[O{{H}^{-}}]\]                    HCl ⇌\[[{{H}^{+}}]\,\,[C{{l}^{-}}]\]                    Total \[[{{H}^{+}}]={{[{{H}^{+}}]}_{{{H}_{2}}O}}+{{[{{H}^{+}}]}_{HCl}}\] \[={{10}^{-7}}+{{10}^{-8}}\]                    \[={{10}^{-7}}[1+{{10}^{-1}}]\]                    \[[{{H}^{+}}]={{10}^{-7}}\times \frac{11}{10}\]\[\]                                 \[pH=-\log \,[{{H}^{+}}]=-\log \left( {{10}^{-7}}+\frac{11}{10} \right)\];\[pH=6.958\]


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