Calculate the mass of phosphorus that must be burned in oxygen to obtain phosphorus oxide (v) with a mass of 3.55 g.

The oxidation reaction of phosphorus to oxygen is described by the following chemical reaction equation.

4P + 5O2 = 2P2O5;

The phosphorus oxide molecule has two phosphorus atoms. Therefore, to obtain one mole of phosphorus oxide, two moles of phosphorus are required.

Let’s find the amount of the substance contained in 3.55 grams of phosphorus oxide.

Its molar mass is.

M P2O5 = 31 x 2 + 16 x 5 = 142 grams / mol;

The amount of the substance will be.

N P2O5 = 3.55 / 142 = 0.025 mol;

Let’s find the mass and amount of the phosphorus substance.

The amount of the substance will be.

N P = N P2O5 x 2 = 0.025 x 2 = 0.05 mol;

M P = 31 grams / mol;

The mass of the substance will be:

m P = 31 x 0.05 = 1.55 grams;