question_answer 1)

What is the pH of 0.001 M aniline solution? The ionization constant of aniline is\[4.27\times {{10}^{-10}}\]. Calculate the degree of ionization of aniline in the solution. Also calculate the ionization of the conjugate acid of aniline.

Answer:

Aniline undergoes dissociation in aqueous medium as follows: \[\underset{{{t}_{\begin{smallmatrix} 0 \\ {{t}_{eq}} \end{smallmatrix}}}}{\overset{{}}{\mathop{{}}}}\,\,\,\,\,\underset{\begin{smallmatrix} C \\ C-C\alpha \end{smallmatrix}}{\mathop{{{C}_{6}}{{H}_{5}}N{{H}_{2}}}}\,+HOH\rightleftharpoons \underset{\begin{smallmatrix} 0 \\ C\alpha \end{smallmatrix}}{\mathop{{{C}_{6}}{{H}_{5}}NH_{3}^{+}}}\,+\underset{\begin{smallmatrix} 0 \\ C\alpha \end{smallmatrix}}{\mathop{O{{H}^{-}}}}\,\] Dissociation constant (\[{{K}_{b}}\]) of aniline may be calculated as: \[{{K}_{b}}=\frac{[{{C}_{6}}{{H}_{5}}N_{3}^{+}][O{{H}^{-}}]}{[{{C}_{6}}{{H}_{5}}N{{H}_{2}}]}=\frac{C\alpha \times C\alpha }{C-C\alpha }\] \[=\frac{C{{\alpha }^{2}}}{1-\alpha }\approx C{{\alpha }^{2}}\] \[(\because \alpha