Q8 / 160 · WBJEE 2011 · Chemistry

The \(\mathrm{pH}\) of an aqueous solution of \(\mathrm{CH}_3 \mathrm{COONa}\) of concentrated \(\mathrm{C}(\mathrm{M})\) is given by

  • A
    \(7-\frac{1}{2} \mathrm{pK}_{\mathrm{a}}-\frac{1}{2} \log \mathrm{C}\)
  • B
    \(\frac{1}{2} \mathrm{pK}_{\mathrm{w}}+\frac{1}{2} \mathrm{pK}_{\mathrm{b}}+\frac{1}{2} \log \mathrm{C}\)
  • C
    \(\frac{1}{2} \mathrm{pK}_{\mathrm{w}}-\frac{1}{2} \mathrm{pK}_{\mathrm{b}}-\frac{1}{2} \log \mathrm{C}\)
  • Correct answer
    D
    \(\frac{1}{2} \mathrm{pK}_{\mathrm{w}}+\frac{1}{2} \mathrm{pK}_{\mathrm{a}}+\frac{1}{2} \log \mathrm{C}\)

Solution

Hints : In case of Hydrolysis of salt of weak acid and strong base, the \(\mathrm{pH}\) is given by \(\frac{1}{2} \mathrm{pK}_{\mathrm{w}}+\frac{1}{2} \mathrm{pK}_{\mathrm{a}}+\frac{1}{2} \log \mathrm{c}\)

Hence, the correct answer is option: 'D'.

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