A solution of Na3PO4 is added dropwise to a solution that is 0.0494 M in Ag+ and 0.00318 M in Cu2+. The Ksp of Ag3PO4 is 8.89e-17. The Ksp of Cu3(PO4)2 is 1.4e-37. (a) What concentration of PO43- is necessary to begin precipitation? (Neglect volume changes.) [PO43-] = M. (b) Which cation precipitates first? Ag+ Cu2+ (c) What is the concentration of PO43- when the second cation begins to precipitate? [PO43-] = M.