Zwitterion is an ion consists of equal positive and negative charges on the same molecule which make it more stable and has high melting point
p-aminobenzene sulfonic acid contains both acidic (-SO₃H) and basic groups (NH₂), the acidic group will lose one proton to give (-SO₃⁻) and the basic group will gain this proton to give (-NH₃⁺)
The structure is:
