1. Write the balanced chemical equation:

N₂ (g) + 3H₂ (g) → 2NH₃ (g)

2. Determine the molar mass of ammonia (NH₃):

* N: 14.01 g/mol

* H: 1.01 g/mol

* NH₃: 14.01 + (3 * 1.01) = 17.04 g/mol

3. Calculate the moles of ammonia:

* Moles = mass / molar mass

* Moles of NH₃ = 63.5 g / 17.04 g/mol = 3.72 mol

4. Use the mole ratio from the balanced equation to find the moles of hydrogen:

* The equation shows that 3 moles of H₂ react to produce 2 moles of NH₃.

* Moles of H₂ = (3 mol H₂ / 2 mol NH₃) * 3.72 mol NH₃ = 5.58 mol H₂

5. Calculate the mass of hydrogen:

* Mass = moles * molar mass

* Mass of H₂ = 5.58 mol * 2.02 g/mol = 11.27 g

Therefore, 11.27 grams of hydrogen must react to produce 63.5 grams of ammonia.