A buffer solution is a solution whose pH remains almost unchanged when a little acid / alkali is added to it.
There are 2 types of buffer sol :
1. Acidic buffer sol
- mixing of a weak acid with salt of the weak acid
- Example : ethanoic acid + sodium ethanoate = acidic buffer sol
- sodium ethanoate is completely ionised in aq sol
- If extra H+ is added, it reacts with CH3COO- to form CH3COOH.
- CH3COOH is a weak acid, thus [H+] of sol remains constant, pH does not change.
- If extra OH- added, it reacts with CH3COOH, thus forming CH3COO- and H2O. Hence, [H+] does not change, pH remanins constant.
2. Alkaline buffer
- mixing of a weak base with salt of the weak base
- Example : ammonia + ammonia chloride = alkaline buffer sol