Question

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

Answer 1

Answer: (D)

$pH=7+\frac{1}{2}\left(pK_{a}-pK_{b}\right)$

$=7+\frac{1}{2}\left(3.2-3.4\right)$

$=6.9$