Calculate the ph of the solution resulting from the addition of 50 ml of 0.10 mol/l h2so4 solution to 50 ml of 0.20 mol/l na3po4 solution.
data: pka1 (h3po4) = 2.15; pka2 (h3po4) = 7.20; pka3 (h3po4) = 12.35