Question

When a salt of weak acid and weak base is dissolved in water at ${25}^{\circ }C$, the $pH$ of the resulting solution will always

• A. be $7$
• B. be greater than $7$
• C. be less than $7$
• D. depend upon $K_a$ and $K_b$ values

Answer 1

The correct option is D depend upon $K_a$ and $K_b$ values

For salts of Weak Acid and Weak Base

Hydrolysis constant $\left(K_h\right)=\frac{K_w}{K_a\times K_b}$,

Degree of hydrolysis, $h=\sqrt{K_h}=\sqrt{\frac{K_w}{K_a\times K_b}}$ when $h<<1$

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