Buffers are the solutions that can resist in change of Ph on dilution and also it can resist on adding small amounts of acids or alkali.
These are extremely useful to maintain constant Ph value as there are a lot of biological and chemical reactions that needs a constant pH for the reaction to proceed.
Due to this buffer solution the pH value will not change as it would be with a solution that is not a buffer.
Types of Buffer Solution:
There are mainly two types of buffer solution:
- Acidic Buffer
- Alkaline Buffer
These are the solutions which have pH value below 7 which contain a weak acid and one of its salts.
A mixture of acetic acid and sodium acetate acts as a buffer solution with a pH of 4.75
These have pH value above 7 and contain weak base and one of its salts.
For example a mixture of ammonium chloride and ammonium hydroxide acts as a buffer solution with pH value of about 9.25
Preparation of Buffer Solution:
Buffer can be prepared either by mixing a weak acid with its conjugate base or weak base with its conjugate acid.
Suppose if you know the pKa (acid dissociation constant) of acid and pKb (base dissociation constant) of the base then you can make a buffer of pH by controlling the ratio of salt and acid or salt and base.
The property of a solution to resist any change in pH value when a small amount of acid or the base is added to it is known as buffer action.
Working of Buffer Action:
For example let us take a mixture of acetic acid (CH3COOH) and sodium acetate (CH3COONa).
Here, the acetic is weakly ionized while sodium acetate is almost ionized.
CH3COOH H+ + CH3COO–
CH3COONa Na+ + CH3COC–
Here if you add a drop of strong acid like HCl, the H+ ions combine with CHCOO– and give CHCOOH and due to this there will be a slight change in its pH value.
CH3COOH + OH– CH3COO– + H2O
Now if you add a drop of NaOH the OH– ions react with the free acid to give undissociated water molecules.
Due to this the OH– ions of NaOH are removed and the value of pH will not change.
Uses of Buffer Solution:
- It is used to regulate the pH of animal blood (it regulates the use of bicarbonate and carbonic acid buffer system).
- It is also used to maintain an optimum pH for enzyme activities in many organisms.
- The absence of these buffers may lead to slowing enzyme action or even denature of enzymes. This process can permanently deactivate the catalytic action of enzymes.