What does a buffer solution do?

A buffer solution plays a crucial role in maintaining pH stability in a system. It is designed to resist changes in pH when small quantities of an acid or base are introduced. This ability arises from the presence of a weak acid and its conjugate base (or a weak base and its conjugate acid) in the solution. When an acid is added, the conjugate base of the buffer reacts with the excess hydrogen ions produced, while the weak acid can release hydrogen ions if a base is added, thus counteracting the changes in pH.

Maintaining a specific pH is essential in many biological and chemical processes, as drastic shifts can lead to adverse effects. For instance, biological systems often require tightly regulated pH levels to function correctly, making buffer solutions vital in both physiological and laboratory settings.

The other options do not accurately describe the primary function of a buffer solution. While a buffer might help maintain a pH close to neutral in some circumstances, it does not guarantee a neutral pH under all conditions. It also does not inherently increase the solubility of salts, nor does it react completely with acids; rather, its role is to minimize pH fluctuations, highlighting its importance in a variety of applications.