What Are Buffers and What Do They Do?

Chemistry of Buffers

A buffer resists changes in pH.
Cl4ss1cr0ck3R / Creative Commons

Buffers are an important concept in acid-base chemistry. Here's a look at what buffers are and how they function.

What Is a Buffer?

A buffer is an aqueous solution that has a highly stable pH. If you add acid or base to a buffered solution, its pH will not change significantly. Similarly, adding water to a buffer or allowing water to evaporate will not change the pH of a buffer.

How Do You Make a Buffer?

A buffer is made by mixing a large volume of a weak acid or weak base together with its conjugate.

A weak acid and its conjugate base can remain in solution without neutralizing each other. The same is true for a weak base and its conjugate acid.

How Do Buffers Work?

When hydrogen ions are added to a buffer, they will be neutralized by the base in the buffer. Hydroxide ions will be neutralized by the acid. These neutralization reactions will not have much effect on the overall pH of the buffer solution.

When you select an acid for a buffer solution, try to choose an acid that has a pKa close to your desired pH. This will give your buffer nearly equivalent amounts of acid and conjugate base so it will be able to neutralize as much H+ and OH- as possible.