Amphoteric salts hydrolysis:

Example of amphoteric salts  NaHS, NaHCO₃, Na₂HPO₄, NaH₂PO₄

(A) HCO3- act as conjugate acid as well as conjugate base:

Both reaction will support each other extent of hydrolysis and extent of dissociation is same.

(B) Here H₂PO₄^- and HPO₄^-2 are amphoteric anions. The pH of amphoteric salts anions is independent of concentration of salts.

Here HPO₄^-2 is conjugate base of H₂PO₄^- and H₃PO₄ is conjugate acid of H₂PO₄^-Similarly PO₄^-3 is conjugate base of HPO₄^-2 and H₂PO₄^-1 is conjugate  acid of HPO₄^-2

When these salts are dissolved in water [H₃O+] concentration can be determined as;

ILLUSTRATIVE EXAMPLE: Calculate pH of solution of

(1) 100 ml 0.1M H₃PO₄ + 100 ml 0.1M NaOH.

(2) 100 ml 0.1M H₃PO₄ + 200 ml 0.1M NaOH.

(3) 100 ml 0.1M H₃PO₄ + 300 ml 0.1M NaOH.

(4) 100 ml 0.1M H₃PO₄ + 400 ml 0.1M NaOH.