Definition of Buffers
A solution which tends to resist changes in pH is called buffer solution.
Preparation of Buffer Solution
Buffer solution of Acetic Acid and Sodium Acetate (Acidic Buffer)
Acetic acid dissociates to give acetate in a follows:
CH3COOH ======== CH3COO– + H+
Sodium acetate dissociates to give also acetate ions as follows:
CH3COONa ======== CH3COO– + Na+
When these two are mixed to make a buffer. There is an increase in the concentration of the acetate ions. Acetic acid equilibrium is pushed to left. So, H+ concentration is reduced and un-dissociated acetic acid is formed and there is no change in pH of the mixture.
Effect of Addition of Acid
In case of added acid, additional H+ ions in the solution will combine acetate ions (CH3COO) to produce un-dissociated acetic acid and pH will remain same.
CH3COO _ + H+ CH3COOH
Effect of Addition of Base
A small amount of base (NaOH) added to the buffer solution will be neutralized by the reaction will weak acid and pH will remain same.
–OH + CH3COOH ======== CH3COO- + H2O
Applications of Buffer
- the use of the buffer is an important part of the many industrial processes, such as electroplating, manufacturing of the leather, etc.
- buffers are used extensively in the analytical chemistry and are used to calibrate pH.
- Human blood is buffered to pH of 7.3. by the means of bicarbonates, phosphates and complex protein system.