Question

2. At a wastewater-treatment plant FeCl3(s) is added to remove excess phosphate from the effluent. Assume that the reactions that occur are FeCl3(s) 5 Fe+ + 3C1 FePO4(s) 5 Fe3+ + PO3- The equilibrium constant for the second reaction is 10-26.4. What concentration of Felt would be needed to maintain the phosphate concentration below the limit of 1 mg/L of P? (Hint: Assume all the P is in the PO form so we're asking for 1 mg/L PO, as P.) Answer: 6.88x10-8 mg/L

Answer 1

we have (k] > [fet] [] X10 Kc = 1X1026.4 ingh of P = 0.001 g/L 30.974 g/mol ? 3.2 285 XIO . _26.4. ...[fe3'] . 1x04 (3.2285x105) . . in a 1:23 x10?? morile 2 1.23x10 22 x 55.845 gle 6.886 x1024 plan riffe3+] = 6.88x10 mg)