When calculating the pH of a buffer solution, what does the term pKa represent?

The term pKa represents the negative logarithm of the acid dissociation constant (Ka) of a weak acid. It is a measure of the strength of the acid in solution and provides insight into how readily the acid donates protons (H+ ions) when dissolved in water. A lower pKa value indicates a stronger acid, which means it more readily dissociates to release hydronium ions (H3O+).

In the context of buffer solutions, the pKa is crucial because it helps in determining the effectiveness of the buffer action. A buffer is typically made from a weak acid and its conjugate base, and the pH of the solution is maintained near the pKa of the weak acid. This close relationship allows the buffer to resist changes in pH when small amounts of acids or bases are added.

Understanding pKa helps predict how the buffer will behave and how effectively it can maintain pH, emphasizing its importance in buffer chemistry.