Explanation:
First conversion factor: moles of SO₄ per mole of Al₂(SO₄)₃.
3 mol SO₄ / mol Al₂(SO₄)₃
Second conversion factor: moles of S per mole of SO₄.
1 mol S / mol SO₄
Altogether:
(3 mol SO₄ / mol Al₂(SO₄)₃) × (1 mol S / mol SO₄) = 3 mol S / mol Al₂(SO₄)₃
