Question

The dissociation constants for aniline, acetic acid and water at ${25}^{\circ }\text{C}$ are $4\times {10}^{-10},2\times {10}^{-5}$ and ${10}^{-14}$ respectively. Calculate degree of hydrolysis of aniline acetate in a decinormal solution.

• A. 0.53
• B. 0.15
• C. 0.35
• D. 0.45

Answer 1

The correct option is A 0.53

$\begin{array}{cccccccccccc}& {\text{Aniline}}^{+}& +& {\text{Acetate}}^{-}& +& H_{2}O& \rightleftharpoons & & & \text{Aniline}& +& Aceticacid\\ \text{Before hydrolysis}& 1& & 1& & & & & & 0& & 0\\ \text{After hydrolysis}& 1-h& & 1-h& & & & & & h& & h\end{array}$
Let, concentration of the salt be $Cmole{\text{litre}}^{-1}$
$K_h=\frac{Ch.Ch}{C(1-h).C(1-h)}=\frac{h^2}{(1-h{)}^2}$
We know, $K_h=\frac{K_w}{K_a{K}_b}$
$\frac{h}{1-h}=\sqrt{\frac{K_w}{K_a.K_b}}=\sqrt{\frac{{10}^{-14}}{2\times {10}^{-5}\times 4\times {10}^{-10}}}$
$\frac{h}{1-h}=1.12$
$\frac{1-h}{h}=0.89$
$\frac{1}{h}=1.89$
$h=0.529$