Question

One of the oxides of iron (FexOy) occurs naturally in the mineral magnetite. When a 2.448 g sample, contain
only magnetite, was analyzed it was found to have 1.771 g of iron. Calculate the empirical formula.

Answer 1

To calculate the empirical formula, we need to determine the ratio of iron to oxygen in the compound.

1. Calculate the molar mass of iron (Fe):
- The atomic mass of iron (Fe) is 55.85 g/mol.

2. Convert the given mass of iron (1.771 g) to moles:
Moles of Fe = mass of Fe / molar mass of Fe
= 1.771 g / 55.85 g/mol
= 0.0317 mol

3. Calculate the molar mass of oxygen (O):
- The atomic mass of oxygen (O) is 16.00 g/mol.

4. Determine the mass of oxygen in the sample:
Mass of O = Mass of sample - Mass of Fe
= 2.448 g - 1.771 g
= 0.677 g

5. Convert the mass of oxygen (0.677 g) to moles:
Moles of O = mass of O / molar mass of O
= 0.677 g / 16.00 g/mol
= 0.0423 mol

6. Determine the ratio of moles of iron to moles of oxygen:
Fe:O = Moles of Fe / Moles of O
= 0.0317 mol / 0.0423 mol
≈ 0.75:1

Therefore, the empirical formula of the oxide of iron is Fe3O4.