If I start Mg + 2HNO3 = Mg(NO3)2 + H2 with 30 grams of Magnesium and an excess of Nitric Acid, how many grams of Hydrogen gas will be made?

Molar mass of Mg = 24.31 g/mol
Molar mass of H₂ = 1.008 × 2 g/mol = 2.016 g/mol

Mg + 2HNO₃ → Mg(NO₃)₂ + H₂
1 mole of Mg reacts to form 1 mole of H₂.

No. of moles of Mg reacted = (30 g) / (24.31 g/mol) = 1.234 mol
No. of moles of H₂ gas made = 1.234 mol
Mass of H₂ gas made = (1.234 mol) × (2.016 g/mol) = 2.49 g