What is the mass (in g) of oxygen in 0.417 mol of Al2(SO4)3?

Answer 1

First, we find the moles of O in 0.417 mols of Al₂(SO₄)₃:

Each 1 mol of Al₂(SO₄)₃ contains 12 mol O (4 x 3 = 12)

0.417 mol Al₂(SO₄)₃ x 12 mol O / mol Al₂(SO₄)₃ = 5.00 mol O

Finally, convert mols of O to grams of O using the atomic mass of O (16 g/mol)

5.00 mol O x 16 g / mol = 80 g O

An alternative approach is;

molar mass Al₂(SO₄)₃ = 342 g / mol

12 O / mol x 16 g / mol O = 192 g O / mol Al₂(SO₄)₃

192 g O / mol Al₂(SO₄)₃ x 0.417 mol Al₂(SO₄)₃ = 80 g of O