Phosphate (POP) is a pollutant from inadequately treated municipal sewage and excess fertilizer usage. Calcium is frequently used to precipitate phosphate in the following reactions: Cas (PO.). (s) 3Ch+ + 2 PO, K = 1 x 10-27 HPO 2H+ +PO, R = 3.98 x 10-13 Phosphorus needs to be in the form of Po, to precipitate with calcium. (a) Determine the pH where 95% of the phosphorus in the second equilibrium equation is in the form of PO, (b) If the phosphate concentration (PO," ) is measured to be 8.5 mg/l at the pH from the provi- ous step, what concentration of calcium (Ca?) would be required in mg/l to remove 95% of the phosphate?