In order to simulate the pH of human blood (pH = 7.4), a buffer solution can be made by dissolving sodium dihydrogen phosphate (NaH2PO4) and sodium hydrogen phosphate (Na2HPO4) in water. The K, of the H2PO4 anion is 6.2 x 10-8 (1) Briefly explain how buffer solutions are able to resist changes in pH when small quantities of strong acids or strong bases are added. (ii) Write a balanced chemical equation for the dissociation of H2PO4 in water. (iii) Determine the mole ratio of Na2HPO4: NaH2PO4 needed to prepare a buffer with a pH of 7.4