01Which form dominates
If pH < pKa, the protonated form (HA) dominates. If pH > pKa, the deprotonated form (A⁻) dominates. At pH = pKa they're equal.
This explains indicator colors and drug absorption.
02Notebook box
Lower pKa = stronger acid.
Worked example: pKa 4.8 in pH 7 blood → mostly A⁻.