Phosphate buffer has 3 ionizable groups, with pKa's of 2.15, 7.2, and 12.45. A 1.20 M solution of this buffer (250 mL) is found to have a pH of 6.0. A biochemist adds 30 mL of 1.0 M NaOH to this buffer.
a) What is the ratio of Na2PO4 to Na2HPO4 at the start of the experiment?
b) What is the resultant pH?
c) how many milliliters of 0.450 M HCl can you add to the final solution in part b) and still maintain as a good phosphate buffer (ie. within 1 pH unit of pKa).