In all the books it is written that a buffer solution can be made with weak acid(e.g.CH3COOH) and strong base (e.g.NaOH).Suppose i have some CH3COOH solution.Then I have foll. equilibriums established:
CH3COOH----><----CH3COO- + H+ -----(1) ---Ka(small) AND
CH3COO-+H20----><----CH3COOH+OH- ----------(2)----Kh(small)
if i add some NaOH then reaction (2) is favoured backwards and almost all of my added NaOH gets converted to acetate ions as 1/Kh is very very large.But then b'coz of increase of acetate ions reaction (1) is favoured and almost all extra ions get converted to acid as 1/Ka is also very very large.
Then increase in acid again causes backward reaction of (2) and ions formed again and the whole process is repeated again and again.So at the end poor OH- is almost negligible.
This is just an example but if we speak in general then i can't maintain a pH of 10,11,etc as then in that case we are assuming [OH]=104etc. which i have proved above is impossible.
Plz give your suggestions on this!!!