Which equation is used to calculate the pH of a buffer solution?

The Henderson-Hasselbalch equation is essential for calculating the pH of a buffer solution because it provides a relationship between the pH, the pKa of the acid, and the concentrations of the acid and its conjugate base. This equation is particularly useful in biochemistry and pharmacology, as it helps to understand the behavior of weak acids and bases in solution, particularly in physiological conditions where maintaining a stable pH is critical.

The equation is formulated as follows:

pH = pKa + log([A⁻]/[HA])

In this context, [A⁻] represents the concentration of the conjugate base, and [HA] represents the concentration of the weak acid. By using this equation, one can determine how the addition of acids or bases to the solution affects the pH, thus ensuring the buffer's efficacy in resisting changes in pH.

Other equations mentioned serve different purposes. Fick's Law relates to diffusion and is thus not applicable to pH calculations. The Nernst equation is used in electrochemistry to calculate the potential of electrochemical cells, and the Michaelis-Menten equation describes the rate of enzyme-catalyzed reactions. Each of these has its specific applications and is unrelated to the