Final answer:
The Henderson-Hasselbalch equation can be used to calculate the pH of both weak acid and weak base buffer solutions, making the original statement false.
Step-by-step explanation:
The statement that the Henderson-Hasselbalch equation is used to calculate the pH of a weak base, but not the pH of a weak acid is false. The Henderson-Hasselbalch equation can be used to calculate the pH of buffer solutions, which consist of a weak acid and its conjugate base, or a weak base and its conjugate acid. This approximation is derived by rearranging the equilibrium constant expression (Ka or Kb) and takes the form of pH = pKa + log([A-]/[HA]) for weak acids or pOH = pKb + log([HB+]/[B]) for weak bases. The equation provides a straightforward method for calculating the pH of a buffer solution, especially when the concentrations of the acid and its conjugate base are comparable.