2. introduction
A buffer solution is one which has the ability to
resist change in pH, on the addition of a small
amount of acid or an alkali or on dilution or on
keeping it for long time.
3. Why does we need it?
Value of pH of purest form of water is 7 but it is
found that when water placed in a glass beaker for
long time is pH value changes because of some
impurities like dissolution of atmospheric carbon
dioxide or slight solubility of the silicates of glass
vessel in water.
4. So what does the above observation
means?
It means the presence of traces of these impurities
changes the pH of water and aqueous solution.
5. Why we need buffer solution
We need it because in many laboratory uses we
requires a solution of constant pH.
7. 1. Acidic buffer
(a)Solution composed of weak acid and is salts
with strong base are acidic buffer viz; solution of
acetic acid and sodium acetate makes a buffer
solution
(b)Solution of concentrated strong acid i.e. HCl ,
H2SO4
8. 2. Alkaline buffer
(a)Solution of weak base and its salt with strong
acid are basic or alkaline buffer viz; a solution of
ammonium hydroxide and its salt NH4Cl
(b)Concentrated solution of strong base and in
water are basic buffers
9. Mechanism of buffer action
(1)Buffering action of a solution of weak acid in
presence of one of its salt with strong base.
CH3COOH⇌ CH3COO- + H-
CH3COONa ⇌ CH3COO- + Na+
↿⇂ H+
CH3COOH
10. (2) buffering action of a solution of a weak base in
presence of its salt with strong acid
NH4OH ⇌ NH4
+ + OH-
NH4CL ⇌ NH4
+ + Cl-
