Question

The dissociation constants of acetic acid and aniline are $1.8\times {10}^{-5}$ and $4.2\times {10}^{-10}$ respectively. What is the degree of hydrolysis of aqueous aniline acetate? What is the pH of the solution?

Answer 1

$Anilin{e}^{+}+Acetat{e}^{-}+H_{2}O\rightleftharpoons Aniline+Aceticacid$

$C$ $C$

$C(1-h)$ $C(1-h)$ $Ch$ $Ch$

$K_h=\frac{K_w}{K_a\times K_b}=\frac{\left(Ch\right)\left(Ch\right)}{C(1-h)C(1-h)}=\frac{h^2}{{(1-h)}^2}$

$\frac{h^2}{{(1-h)}^2}=K_h=1.3$

$\frac{h}{(1-h)}=1.14$

$h=0.53$

$pH$ for hydrolysis of salt of weak acid and weak base is given by:

$pH=7+0.5(p{K}_a-p{K}_b)$

$pH=7+0.5(4.74-9.37)=4.68$