How can develop the Henderson-Hasselbalch equation for buffers starting from a buffer solution that contains a weak acid (HA) and its conjugate base (A-)? Suppose you may assume that the weak acid has a Ka 10-5 or less. For simplicity, set the initial molar concentration for the weak acid to be X and the initial molar concentration of A- to be Y. Based on the derivation, determine the assumptions when deriving the Henderson Hasselbalch equation for buffers.