ABSTRACT
Definition of a buffer solution Aqueous solutions of sodium chloride and of ammonium acetate are neutral; they display pH 7. Sodium chloride is the salt of a strong acid (HCl) and a strong base (NaOH), hence hydrolysis does not occur (Section N3). In contrast ammonium acetate is the salt of a weak acid and a weak base; as their strengths are almost equivalent such a solution is almost neutral (Section N3). However, the differing nature of the acids and bases in the
two solutions (that is their differing responses to neutralization) means that they respond differently to the addition of small quantities of acid or base. If a small amount of hydrochloric acid is added to the sodium chloride solution, the pH of the solution will drop markedly. In contrast, if the same amount of acid is added to a solution of ammonium acetate, the pH remains virtually unchanged. Ammonium acetate is thus said to display buffer action, and the solution of ammonium acetate is known as a buffer solution.
