CHEMISTRY HELP PLEASE: acids and bases?

Question

A) Calculate the pH of a buffer solution that contains 0.60 M NaH2PO4, and 0.15 M Na2HPO4.

B) What volume (L) of 0.408 M potassium hydroxide solution would just neutralize 100.6 ml of 0.380 M H2SO4 solution?

Answer 1

A) Since both the acid (H2PO4-) and the base (HPO42-) are present, you can just use Henderson-Hasselbach. You will need the SECOND Ka of H3PO4 (why?)

B) Balancing: moles OH- = moles H+. So

V x 0.408 M NaOH x 1 OH-/NaOH = 100.6 mL x 0.380M H2SO4 x 2 H+/H2SO4