Question

Phosphate rock contains 80 percent of the compound 3Ca3(PO4)2.CaF2. (a) How much phosphorous is contained in 100 lb of phosphate rock? (b) How much equivalent phosphorous pentoxide P2O5 is contained in 100 lb of phosphate rock?

Answer 1

Ans. #1. Given- Mass of phosphate rock = 100 lb = 45.3592 kg = 45359.2 g

# Mass of Ca₃(PO₄)₂.CaF₂ in phosphate rock = 80% of 45359.2 g = 36287.36 g

# 1 mol Ca₃(PO₄)₂.CaF₂ (MW = 388.2515304 g/ mol) consists of 1 mol P (MW = 30.973762 g/ mol). So, 388.2515304 g Ca₃(PO₄)₂.CaF₂ is equivalent to 30.973762 g P.

So,

Mass of P = (30.974 g P / 388.25 g Ca₃(PO₄)₂.CaF₂) x 36287.36 g Ca₃(PO₄)₂.CaF₂

                        = 2894.92 g = 2.89492 kg = 6.382 lb

#2. 1 mol Ca₃(PO₄)₂.CaF₂ (MW = 388.2515304 g/ mol) consists of 1 mol P₂O₅ (MW = 141.944524 g/ mol). So, 388.2515304 g Ca₃(PO₄)₂.CaF₂ is equivalent to 141.944524

g P₂O₅.

So,

Mass of P = (141.945 g P₂O₅ / 388.25 g Ca₃(PO₄)₂.CaF₂) x 36287.36 g Ca₃(PO₄)₂.CaF₂

                        = 13266.724 g = 13.267 kg = 29.25 lb