H3PO4 undergoes three ionization equilibria, for each ionization pka's 2.12, 7.21, and 12.3 respectively. A solution formed by mixing 100 mL of 0.1 M NaH2PO4 and 100 mL of 0.1 M Na2HPO4 now you just need to calculate the pH of this solution? if we want to lower the pH by one unit of this solution then How many mL of 0.1 M H3PO4 should be added to this solution?