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)`.

Explanation

`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`