CET Karnataka Medical CET - Karnataka Medical Solved Paper-2010

  • question_answer
    A buffer solution contains \[0.1mole\]of sodium acetate in \[1000c{{m}^{3}}\]of \[0.1M\]acetic acid. To the above buffer solution, \[0.1mole\] of sodium acetate is further added and dissolved. The pH of the resulting buffer is equal to

    A)  \[p{{K}_{a}}-\log 2\]

    B)  \[p{{K}_{a}}\]

    C)  \[p{{K}_{a}}+2\]       

    D)  \[p{{K}_{a}}+\log 2\]

    Correct Answer: D

    Solution :

    Initially \[[C{{H}_{3}}COONa]=0.1mol\] \[[C{{H}_{2}}COOH]=0.1mol\] when  \[0.1mol\,C{{H}_{3}}COONa\] is added. \[[C{{H}_{3}}COONa]=0.1+0.1=0.2mol\] \[pH=p{{K}_{a}}+\log \frac{[salt]}{[acid]}\] \[=p{{K}_{a}}+\log \frac{0.2}{0.1}\] \[=p{{K}_{a}}+\log 2\]


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