It has been found that the pH of a 0.01 M solution of an organic acid is 4.15. Calculate the concentration of the anion, the ionization constant of the acid and its pK_(a).

It has been found that the pH of a 0.01 M solution of an organic acid

1.	It has been found that the pH of a 0.01 M solution of an organic acid is 4.15. Calculate the concentration of the anion, the ionization constant of the acid and its pK_(a).
Answer» Solution :`HA hArr H^(+) + A^(-)` `pH = - log [H^(+)] or log [H^(+)]= - pH = - 4.15 = BAR(5) . 85` `:. [H^(+)]=7.08 XX 10^(-5)M = 7.08xx10^(-5)M` `[A^(-)]=[H^(+)]=7.08xx10^(-5)M` `K_(a)=([H^(=)][A^(-)])/([HA])=((7.08xx10^(-5))(7.08xx10^(-5)))/(10^(-2))=5.0 xx10^(-7)` `pK_(a)=-log K_(a) = - log (5.0xx10^(-7))= 7-0.699=6.301`