Ionic Equilibria of Buffer Systems

A buffer can be defined as a solution that maintains an approximately equal pH value even if small amounts of acidic or basic substances are added. To function in this manner, a buffer solution will necessarily contain either an acid and its conjugate base, or a base and its conjugate acid.

The action of a buffer system can be understood through the use of a practical example. Consider acetic acid, for which KA = 1.82 x 10-5 (pK = 4.74). The following pH values can be calculated (for solutions having a total acetate content of 1.0 M) using its acid ionization constant expression:

Acetic Acid, [HA]

Acetate Ion, [A ]

Calculated pH

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