JEE Main & Advanced Chemistry Equilibrium / साम्यावस्था Question Bank Critical Thinking

  • question_answer
    \[p{{K}_{a}}\]of acetic acid is \[4.74\]. The concentration of \[C{{H}_{3}}COONa\] is 0.01 M. The pH of \[C{{H}_{3}}OONa\]is [Orissa JEE 2004]

    A)                 3.37       

    B)                 4.37

    C)                 4.74       

    D)                 0.474                

    Correct Answer: A

    Solution :

               \[{{H}^{+}}=c\,.\,\alpha =\sqrt{{{K}_{a}}\,.\,c}\]                    \[pH=-\log {{\left( \sqrt{{{K}_{a}}.\,c} \right)}^{1/2}}\]\[=\frac{1}{2}[-\log {{K}_{a}}-\log c]\]                                 \[=\frac{1}{2}[4.74-\log {{10}^{-2}}]\]\[=\frac{1}{2}[4.74+2]=3.37\].


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