What is the equation used to calculate pH in a buffer solution?

In a buffer solution, the pH is calculated using the Henderson-Hasselbalch equation, which is a fundamental relationship in acid-base chemistry. The correct equation relates the pH of the solution to the pKa of the weak acid and the ratio of the concentrations of the conjugate base and the weak acid.

The format of the equation is pH = pKa + log ([conjugate base]/[weak acid]). This properly expresses how the pH of the buffer solution is influenced by the ratio of the concentration of the conjugate base to the concentration of the weak acid. When the concentration of the conjugate base increases relative to the weak acid, the pH of the solution will rise, indicating a more basic environment. Conversely, if the concentration of the weak acid is greater, the pH will decrease, indicating a more acidic environment.

Using the correct relationship is critical for determining how the pH will adjust in response to added acids or bases in a buffer system, showcasing the buffer’s ability to maintain a relatively stable pH.