Sulfur Trioxide + water

Sulfur Trioxide + water ➜ Sulfuric Acid
SO₃(g) + H₂O(l) ➜ H₂SO₄(aq)

SO₃ = 80 g/mol
H₂O = 18 g/mol
H₂SO₄ = 98 g/mol

1 mol of SO₃ + 1 mol of H₂O ➜ 1 mol of H₂SO₄
80 g of SO₃ + 18 g of H₂O ➜ 90 g of H₂SO₄