A115.0-g sample of iron (fe) is burned in excess oxygen. the result is a pure solid with a mass of 164.5 grams. what is the empirical formula of the solid?

The empirical formula is Fe2O3

Explanation:

Step 1: Data given

Mass of the iron sample = 115.0 grams

Mass of the pure solid = 164.5 grams

Molar mass of Fe = 55.845 g/mol

Molar mass of O = 16 g/mol

Step 2: Calculate mass of oxygen

mass of oxygen = mass of solid - mass of iron

Mass of oxygen = 164.5 grams - 115.0 grams

MAss of oxygen = 49.5 grams

Step 3: Calculate moles of oxygen

Moles oxygen = mass oxygen / molar mass oxygen

Moles oxygen = 49.5 grams / 16.0 g/mol

Moles oxygen = 3.09 moles

Step 4: Calculate moles of Fe

Moles Fe = mass Fe / molar mass Fe

Moles Fe = 115.0 grams / 55.845 g/mol

Moles Fe = 2.06 moles

Step 5: Calculate mol ratio

We divide by the smallest amount of moles

O: 3.09/2.06 = 1.5

Fe: 2.06 / 2.06= 1

This means for 1  mol Fe we have 1.5 mol O  OR for each 2 moles Fe we have 3 moles O.

The empirical formula is Fe2O3