The majority of industrial method for the preparation of elemental phosphorus is heating a mixture of phosphate rock, carbon, and sand in electric furnace. The chemical reactions can be represented by 2Ca3(PO4)2 + 6SiO2 ? 6CaSiO3 + P4O10 and P4O10 + 10C ? P4 + 10CO Then calculate the percentage of Ca3(PO4)2 initially present in the rock sample if 307kg of phosphate rock yields 42.5kg of elemental P4.