At a waste water treatment plant, Fe3Cl3 is added to remove excess phosphate from the effluent. Assume the following reactions occur:
FeCl3 -> Fe 3+ + 3 Cl-
Fe 3+ + PO43- -> Fe PO4
The equilibrium constant for the second reaction is 10^26.4. Ksp = 10^-26.4 for the reverse reaction. What concentration of Fe3+ is needed to maintain the phosphate concentration below the limit of 1 mg P/L?