Final answer:
After adding a small amount of acid to a buffer with an initial pH of 5.25, a reasonable pH value would be 5.15, illustrating the buffer's ability to resist pH changes by neutralizing the added acid without significantly altering the pH.
Step-by-step explanation:
The question addresses the concept of pH buffers and the change in pH that would result from the addition of a small amount of acid to a buffer system. In this scenario, a buffer containing equal amounts of a weak acid and its conjugate base, with an initial pH of 5.25, is considered. The addition of a small amount of acid to this buffer will result in a slight decrease in the pH. A reasonable value of the buffer pH after such an addition would be 5.15, not too far from the initial pH, reflecting the buffer's capacity to minimize pH changes.
Buffers are most effective when the concentrations of the weak acid (HA) and its conjugate base (A-) are equal, as this allows them to neutralize added bases or acids effectively. The pH of a buffer depends largely on the ratio of the concentrations of the conjugate base to the acid and also on the pKa of the weak acid involved. According to the Henderson-Hasselbalch equation, when the concentrations of HA and A- are equal, the pH will be equal to the pKa.