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NEET Sample Paper NEET Sample Test Paper-7

  • question_answer
    The dissociation constant of acetic acid \[{{K}_{a}}\] is \[1.74\times {{10}^{-5}}\]at 29 K. The pH of a solution of \[0.1\text{ }M\]acetic acid is:

    A)  \[2.88\]                       

    B)  \[3.6\]

    C)  \[4.0\]                         

    D)  \[1.0\]

    Correct Answer: A

    Solution :

    For \[0.1\text{ }M\] acetic acid or \[C=0.1\,M{{L}^{-1}}\] \[{{K}_{a}}=1.74\times {{10}^{-5}}\] According to ostwald dilution formula             \[[{{H}^{+}}]=\sqrt{{{K}_{a}}.C}\] \[=\sqrt{1.7\times {{10}^{-5}}\times 0.1}\] \[=\sqrt{0.017\times {{10}^{-4}}}\] \[pH=-{{\log }_{10}}[{{H}^{+}}]\] \[=-{{\log }_{10}}\left[ \sqrt{0.017\times {{10}^{-4}}} \right]\] \[pH=2.88\].


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