CHEM BRAIN

A solution whose pH is not altered to any great extent by the addition of small quantities of either sirong acid (H+ ions) or a sirong base (OH– ions) is called the buffer solution. It can also be defined as a solution of reserve acidity or alkalinity which resists change of pH upon the addition of small amount of acid or alkali. ?

 Acidic buffer : It is the solution of a mixture of a weak acid and a salt of this weak acid with a strong base. Example : CH₃COOH + CH₃COONa

• (i) Phthalic acid + potassium hydrogen phthalate
• (ii) Citric acid + sodium citrate.
• (iii) Boric acid + borax (sodium tetraborate).
• (iv) Carbonic acid ( ) H2CO3 + sodium hydrogen carbonate ( NaHCO3) . This system is found in blood and helps in maintaining pH of the blood close to 7.4 ( pH value of human blood lies between 7.36 – 7.42; a change in pH by 0.2 units may cause death).
• (v) NaH2PO4 + Na3PO4
• (vi) NaH2PO4 + Na2HPO4
• (vii) Glycerine + NaOH

 Basic buffer : It is the solution of a mixture of a weak base and a salt of this weak base with a strong acid. 

• Ammonium hydroxide + Ammonium chloride
•  Glycerine + Hydrochloric acid

 Buffer action is the mechanism by which added H+ ions or OH– ions are almost neutralised