Question

$p{K}_a$ of a weak acid $\left(HA\right)$ and $p{K}_b$ of a weak base $\left(BOH\right)$ are $3.2$ and $3.4$, respectively. The $pH$ of their salt $\left(AB\right)$ solution is :

• A. $6.9$
• B. $7.0$
• C. $1.0$
• D. $7.2$

Answer 1

Answer: (A)

$6.9$

We know,

$pH=\frac{1}{2}(p{K}_w+p{K}_a-p{K}_b)$

$pH=\frac{1}{2}(14+3.2-3.4)$

$pH=\frac{1}{2}\left(13.8\right)$

$pH=6.9$

Hence, the option (A) is the correct answer.