Which species can act as both a Bronsted-Lowry acid and base?
H₂PO₄- can donate H+ (acid) to form HPO₄²⁻ or accept H+ (base) to form H₃PO₄ , making it amphoteric.
Ref: NCERT Class 11 Chemistry > Chapter 6: Equilibrium > Topic: Acid-Base Theories - Arrhenius Bronsted-Lowry Lewis and Salts Hydrolysis
