A geologist is analyzing a sample of phosphate rock to determine its suitability for fertilizer production. One of the primary minerals in the rock is calcium phosphate, Ca3(PO4)2\text{Ca}_3(\text{PO}_4)_2Ca3(PO4)2.
Calculate the percentage by mass of phosphorus in calcium phosphate, Ca3(PO4)2\text{Ca}_3(\text{PO}_4)_2Ca3(PO4)2.
percentage by mass of element=total relative atomic mass of elementrelative formula mass of compound×100 \text{percentage by mass of element} = \frac{\text{total relative atomic mass of element}}{\text{relative formula mass of compound}} \times 100 percentage by mass of element=relative formula mass of compoundtotal relative atomic mass of element×100(relative atomic masses: O=16\text{O} = 16O=16, P=31\text{P} = 31P=31, Ca=40\text{Ca} = 40Ca=40)
258 exam-style questions on Edexcel GCSE Chemistry Calculations involving masses. Each one has a worked solution and a mark scheme showing where the marks go.