Question

The dissociation constants for aniline, acetic acid and ionic product of water at $25^{\circ} C$ are $3.83 \times 10^{-10}, 1.75 \times 10^{-5}$ and $1.008 \times 10^{-14}$ respectively. The degree of hydrolysis of aniline acetate in a decinormal solution is

• A. $0.56 \%$
• B. $55 \%$
• C. $5.6 \%$
• D. $2.75 \%$

Answer 1

Answer: (B)

Let the concentration of salt be $C $ mol $ lit ^{-1}$
$K _{ h }=\frac{\left[ C _{6} H _{5} NH _{2}\right]\left[ CH _{3} COOH \right]}{\left[ C _{6} C _{5} NH _{3}^{+}\right]\left[ CH _{3} COO ^{-}\right]} $
$=\frac{ C ^{2} h ^{2}}{ C ^{2}(1- h )(1- h )}=\frac{ h ^{2}}{(1- h )^{2}} $
$\sqrt{ K _{ h }}=\frac{ h }{(1- h )} $
Or $ \left(\frac{ h }{1- h }\right)=\sqrt{ K _{ h }}=\sqrt{\frac{ K _{ w }}{ K _{ a } \cdot K _{ b }}}$
$=\sqrt{\frac{1.008 \times 10^{-14}}{1.75 \times 10^{-5} \times 3.83 \times 10^{-10}}}$
$=\sqrt{\frac{1.008 \times 10}{1.75 \times 3.83}}=\sqrt{\frac{10.08}{6.7025}}=\sqrt{1.5039}$
$\left(\frac{ h }{1- h }\right)=1.23$
or $h =0.55$
$h =0.55$
or $55 \%$