Find the mass of burned phosphorus if 22.27 grams of P2O5 is formed.

We compose the reaction equation and arrange the coefficients:
4P + 5O2 = 2P2O5.
1) Find the molar mass of phosphorus oxide according to the periodic table: 31 * 2 + 16 * 5 = 142.
2) Find the amount of phosphorus oxide substance. To do this, divide the mass of the oxide by the molar mass: 22.27 / 142 = 0.16 mol.
3) According to the reaction equation, there are four moles of phosphorus for two moles of phosphorus oxide. This means that the amount of phosphorus substance is: 2 * 0.16 / 4 = 0.08 mol.
4) Molar mass of phosphorus: 31.
5) Find the mass of phosphorus. To do this, we multiply the amount of phosphorus by its molar mass: 31 * 0.08 = 2.48 g – the answer.