How many grams of hydrogen (H2) are required to produce 81.6g of NH3?

Molar mass of H₂ = 1.0×2 g/mol = 2.0 g/mol
Molar mass of NH₃ = (14.0 + 1.0×3) = 17.0 g/mol

N₂(g) + 3H₂(g) → 2NH₃(aq)
OR: Mole ratio H₂ : NH₃ = 3 : 2

No. of moles of NH₃ produced = (81.6 g) / (17.0 g/mol) = 4.8 mol
No. of moles of H₂ required = (4.8 mol) × (3/2) = 7.2 mol
Mass of H₂ required = (2.0 g/mol) × (7.2 mol) = 14.4 g

81.6 X (3/17) <<< use a calculator