MCQ
$pK_a$ of a weak acid $(HA)$ and $pK_b$ of a weak base $(BOH)$ are $3.2$ and $3.4,$ respectively. The $pH$ of their salt $(AB)$ solution is
- A$7.2$
- B$6.9$
- ✓$7.0$
- D$1.0$
✓
Answer
Correct option: C.
$7.0$
c
For the salt of weak acid and weak base, we have
For the salt of weak acid and weak base, we have
$\mathrm{pH} =7+\frac{1}{2} \mathrm{p} K_{\mathrm{a}}-\frac{1}{2} \mathrm{p} K_{\mathrm{b}} $
$=7+\frac{1}{2}(3.2)-\frac{1}{2}(3.4) $
$=6.9$
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