1. Determine the Mass of Oxygen

* The mass of oxygen that reacted with the iron is the difference between the mass of the oxide and the mass of the iron:

* Mass of oxygen = 118.37 g - 85.65 g = 32.72 g

2. Convert Masses to Moles

* Iron (Fe):

* Molar mass of Fe = 55.845 g/mol

* Moles of Fe = (85.65 g) / (55.845 g/mol) = 1.534 mol

* Oxygen (O):

* Molar mass of O = 16.00 g/mol

* Moles of O = (32.72 g) / (16.00 g/mol) = 2.045 mol

3. Determine the Empirical Formula

* Divide the number of moles of each element by the smallest number of moles to get the simplest whole-number ratio:

* Fe: 1.534 mol / 1.534 mol = 1

* O: 2.045 mol / 1.534 mol = 1.33

* Since we need whole numbers, multiply both ratios by 3 to get:

* Fe: 3

* O: 4

4. The Empirical Formula

* The empirical formula of the iron oxide is Fe₃O₄.

Note: This is the formula for a specific iron oxide called magnetite.