For an organic monoprotic acid solution of concentration Co mole `litre^(-1)`, if `K_(a)` has a value comparable to `K_(w)`, show that the hydronium ion concentration is given by :
`[H^(+)]= [(K_(w))/(H(+)]+(K_(a).Co)/([K_(a)+H^(+)])]`
If `[H^(+)]=10^(-3)M` and `Co=10^(-1)M` in a solution of some organic monoprotic acid, what according to the above equation must be the order of magnitude of `K_(a)` ?

Answer

`10^(-5);`