A 1.45 g sample of phosphorus burns in air and forms 2.57 g of a phosphorus oxide. Calculate the empirical formula of the oxide. Express your answer as a chemical formula.

P2O3

Explanation:

Firstly, we know that the phosphorus would absorb oxygen from air to form its oxide. We already know the mass of the phosphorus, we can get the mass of the oxygen by subtracting the mass of the phosphorus from the mass of the oxide.

The mass of the oxygen is 2.57 - 1.45 = 1.12g

From here, we covert these masses to moles by dividing by the atomic masses of phosphorus and oxygen respectively.

The atomic mass of phosphorus is 31 while that of oxygen is 16.

P = 1.45/31 = 0.046774193548

O = 1.12/16 = 0.07

We now divide by the smallest which is that of phosphorus.

P = 0.046774193548 / 0.046774193548 = 1

O = 0.07 / 0.046774193548 = 1.5

We then multiply the answers by 2 for conversion to whole numbers. Making P = 2 and O = 3

The empirical formula is thus P2O3