Q35 / 105 · JEE Main 2008 · Chemistry

The $\mathrm{pK}_{\mathrm{a}}$ of a weak acid, $\mathrm{HA}$, is $4.80$. The $\mathrm{pK}_{\mathrm{b}}$ of a weak base, $\mathrm{BOH}$, is $4.78$. The $\mathrm{pH}$ of an aqueous solution of the corresponding salt, BA, will be

  • A
    $9.58$
  • B
    $4.79$
  • Correct answer
    C
    $7.01$
  • D
    $9.22$

Solution

It is a salt of weak acid and weak base $$ \begin{aligned} & {\left[\mathrm{H}^{+}\right]=\sqrt{\frac{\mathrm{K}_{\mathrm{w}} \times \mathrm{K}_{\mathrm{a}}}{\mathrm{K}_{\mathrm{b}}}}} \\ & \mathrm{pH}=7.01 \end{aligned} $$

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

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