Answer:
H₃PO₄ is an acid because donates the proton to fenolate.
Fenolate is the base because accepts the proton from the acid.
Explanation:
Bronsted theory mentioned that acid is the one that donates a proton to another compound and base is the one that receives it.
H₃PO₄ + C₆H₅O⁻ ⇄ H₂PO₄⁻ + C₆H₅OH
acid base conj. base conj. acid
H₃PO₄ is an acid because donates the proton to fenolate.
Fenolate is the base because accepts the proton from the acid.
If we follow the dissociation, the diacid phosphate can donate two more protons, it is still a Bronsted acid, but it can act as an acid or a base. This is called amphoteric.
