A 30-mL volume of a K2HPO4 solution containing 50-mg P/L is placed in contact with 40g of soil (dry weight basis) in a centrifuge tube. After a 7-d equilibration period, the suspension is centrifuged to separate the equilibrium solution from the soil. A 5-mL aliquot of this equilibrium solution is diluted with 45 mL of a 10mM CaCl2 solution. The diluted solution is analyzed for P and found to contain 1.0 mg P/L. Answer the following:

What is the concentration of P retained in the soil (in mg P/kg)?

What is the concentration of PO4 retained by the soil (in mg PO4/kg)?

What was the molecular concentration of P in the initial solution (before placing in contact with the soil)?

What was the molecular concentration of K2HPO4 in the initial solution?