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AIIMS AIIMS Solved Paper-2002

  • question_answer
    At \[{{25}^{o}}C\] the pH of a solution containing 0.10 M sodium acetate and 0.03 M acetic acid is: [\[_{p}{{K}_{a}}\] value of \[C{{H}_{3}}COOH=4.57\]]

    A)  \[3.24\]              

    B)         \[4.59\]              

    C)         \[5.09\]              

    D)         \[6.67\]

    Correct Answer: D

    Solution :

    The mixture consist of weak acid and its salt with strong base, so it acts as a acidic buffer solution. According to Henderson Hasselbalch equation \[pH{{=}_{p}}{{K}_{a}}+\log \frac{[salt]}{[acid]}\] \[=4.57+\log \frac{0.10}{0.03}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,[\log 3=0.4771]\] \[pH=4.57+2.095=6.67\]


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