Buffer Capacity
- Buffer capacity: represents the amount of H+ or OH- the buffer can absorb without a significant change in pH
- The pH of a buffered solution is determined by the ratio of [A-]/[HA]
- Same ratio = same pH
- The buffer capacity is determined by the [A-] & [HA]
- More moles = greater capacity
- Less moles = less capacity bcuz there is less buffer to react with
How to Choose a Buffer
- The most effective buffers (most resistant to change) have a ratio of [A-]/[HA] = 1
- Is true when [A-] = [HA] → This means that pH = pKa (since log 1 = 0)
- When choosing a buffer for a desired pH, choose the buffer system whose pKa is closest to the desired pH
- The log of a larger number is less negative than the log of a smaller number → higher pH