Chemistry Confused

Two Concept Questions for you: 1) Why is the concentration of a solution such as NaH2PO4 ignored when calculating the pH given Ka1, Ka2, and K3 values? 2) Given Pka1=3.13, Pka2=4.76, and Pka3 = 6.40, calculate the pH of lemon juice which is about 5% citri...

What must be the pH of a solution that is 0.049 M Fe3+ to just cause Fe(OH)3(s) to precipitate?

Calculate the molar solubility of barium thiosulfate in 0.0045 M Na2S2O3(aq). (Hint: Check any simplifying assumptions that you make.)