WB JEE Medical WB JEE Medical Solved Paper-2011

  • question_answer
    The pH of an aqueous solution of \[C{{H}_{3}}COONa\]of concentration C(M) is given by

    A)  \[7-\frac{1}{2}p{{K}_{a}}-\frac{1}{2}\log \,C\]

    B)  \[\frac{1}{2}p{{K}_{w}}+\frac{1}{2}p{{K}_{b}}+\frac{1}{2}\log \,C\]

    C)  \[\frac{1}{2}p{{K}_{w}}-\frac{1}{2}p{{K}_{b}}-\frac{1}{2}\log \,C\]

    D)  \[\frac{1}{2}p{{K}_{w}}+\frac{1}{2}p{{K}_{a}}+\frac{1}{2}\log \,C\]

    Correct Answer: D

    Solution :

                     \[C{{H}_{3}}COONa+{{H}_{2}}O\underset{s}{\mathop{C{{H}_{3}}COOH}}\,\]\[+\underset{\text{Strong}\,\text{base}}{\mathop{NaOH}}\,\] As sodium acetate is a salt of weak acid and strong base, in hydrolysis of sodium acetate the pH is given by \[pH=\frac{1}{2}p{{K}_{w}}+\frac{1}{2}p{{K}_{a}}+\frac{1}{2}\log C\]


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