The Henderson-Hasselbalch equation is used to calculate the pH of a weak base, but not the pH of a weak acid.
A buffer's capacity to neutralize added acid depends on the number of moles of weak acid the buffer contains.
The difference in composition between a weak base and its conjugate acid is
1. 1 H+
2. 2 H+
3. 1 OH-
4. 2 OH-