question_answer 1)

The ionisation constant of acetic acid is\[1.74\times {{10}^{-5}}\]. Calculate the degree of dissociation of acetic acid in its 0.05 M solution. Calculate the concentration of acetate ion in the solution and its\[pH\].

Answer:

Acetic acid is a weak acid, it undergoes ionisation in aqueous medium as follows: \[\underset{\begin{smallmatrix} t=0 \\ {{t}_{eq}} \end{smallmatrix}}{\overset{{}}{\mathop{{}}}}\,\,\,\,\,\underset{\begin{smallmatrix} C \\ C-C\alpha \end{smallmatrix}}{\mathop{C{{H}_{3}}COOH(aq)}}\,\rightleftharpoons \underset{\begin{smallmatrix} 0 \\ C\alpha \end{smallmatrix}}{\mathop{C{{H}_{3}}CO{{O}^{-}}(aq)}}\,+\underset{\begin{smallmatrix} 0 \\ C\alpha \end{smallmatrix}}{\mathop{{{H}^{+}}(aq)}}\,\] where \[\alpha \]is degree of ionisation. \[{{K}_{a}}=\frac{[C{{H}_{3}}CO{{O}^{-}}][{{H}^{+}}]}{[C{{H}_{3}}COOH]}=\frac{C\alpha \times C\alpha }{C-C\alpha }\] \[{{K}_{a}}=\frac{C{{\alpha }^{2}}}{(1-\alpha )}\] \[\because a