Gr.11 chemistry emperical formula?

Question

help me answer this T^T i dont kno what to do because the mass and other info arnt given!

The following equation shows the formation of phosphorus(V) oxide:

4P(s) + 5O2 (g) -> 2 P2O5 (s)

a) write the mole ratios that can be derived from this equation.

b) calculate the amount of phosphorus that is needed to form 4.5 mol P2O5

Answer 1

The mole ratios come from the coefficients in the balanced chemical equation.

4P(s) + 5O2 (g) -> 2 P2O5 (s)

P:O2:P2O5

4:5:2

or

4 mol P / 5 mol O2

2 mo P / 1 mol P2O5

5 mol O2 / 2 mol P2O5

4.5 mol P2O5 x (2 mol P / 1 mol P2O5) = 9.0 mol P2O5