Question

The $p{K}_a$ of a weak acid, $HA$, is 4.80 and the $p{K}_b$ of a weak base, $BOH$, is 4.78. The pH of an aqueous solution of the corresponding salt, $BA$, will be:

• A. 8.58
• B. 4.79
• C. 7.01
• D. 9.22

Answer 1

The correct option is C 7.01

Let, the salt of weak acid and base like $C{H}_{3}COON{H}_4$

Now,

Salt hydrolysis formula is:

$K_h=\frac{K_w}{K_a{K}_b}$

$h=\sqrt{\frac{K_w}{K_a{K}_b}}$

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

So, $pHof$Salt is,

$pH=\frac{1}{2}(14+4.80-4.78)$

$=7.01$

This is the required solution.