A sample of hematite contains 34.97 g of iron and 15.03 g of oxygen. What I’d the empirical formula?

Answer 1

To determine the empirical formula, we need to find the ratio of the number of atoms of each element present in the compound.

1. Convert the mass of each element into moles:
Given:
Mass of iron (Fe) = 34.97 g
Mass of oxygen (O) = 15.03 g

Molar mass of iron (Fe) = 55.85 g/mol
Molar mass of oxygen (O) = 16.00 g/mol

Number of moles of iron (Fe) = mass of iron / molar mass of iron
= 34.97 g / 55.85 g/mol
≈ 0.626 mol

Number of moles of oxygen (O) = mass of oxygen / molar mass of oxygen
= 15.03 g / 16.00 g/mol
≈ 0.939 mol

2. Divide the number of moles of each element by the smallest number of moles calculated. In this case, the smallest number of moles is 0.626, so we divide both the number of moles by this value.

Number of moles of iron (Fe) = 0.626 mol / 0.626 mol
= 1 mol

Number of moles of oxygen (O) = 0.939 mol / 0.626 mol
≈ 1.5 mol

3. Multiply each element's mole ratio by a common factor if necessary to obtain whole numbers.

Going back to the number of moles ratio:
Fe:O = 1:1.5
Multiply by 2 to eliminate fractions:

Fe:O = 2:3

4. Write the empirical formula using the ratio obtained:
Fe2O3

So, the empirical formula of the compound is Fe2O3, which represents hematite.