Chapter 17.1: Introduction to Buffer Solutions

Regulation of pH is critical to

the survival of organisms

Solution pH is controlled via the presence of

one or more buffer solutions.

Buffer solutions resist changes in pH by neutralizing added acid or base, and are

governed by the common-ion effect.

In aqueous solution, nitrous acid, HNO2, a weak acid, ionizes,

producing small equilibrium concentrations of nitrite ion and hydronium ion.

However, adding the strong electrolyte sodium nitrite, NaNO2, to the solution provides additional NO2− and

shifts the equilibrium toward the reactants, suppressing the ionization of HNO2.

This suppression of ionization of a weak electrolyte when combined with a strong electrolyte containing a common ion is known as the

common-ion effect

A solution containing both a weak acid and its conjugate base is called a

Buffer Solution

Buffer solutions….

resist a change in pH, even when an appreciable quantity of a strong acid or strong base is added.

A buffer has significant quantities of both HA and its conjugate base, A−, allowing it to

shift in either direction when either acid or base is added.