1. Write the Balanced Chemical Equation:

The reaction of ammonia (NH₃) with oxygen (O₂) produces nitrogen gas (N₂) and water (H₂O):

4 NH₃ + 5 O₂ → 4 NO + 6 H₂O

2. Calculate the Molar Mass of Ammonia and Oxygen:

* Molar mass of NH₃ = 14.01 g/mol (N) + 3(1.01 g/mol) (H) = 17.04 g/mol

* Molar mass of O₂ = 2(16.00 g/mol) (O) = 32.00 g/mol

3. Convert Grams of Ammonia to Moles:

* Moles of NH₃ = (200.0 g NH₃) / (17.04 g/mol NH₃) = 11.74 mol NH₃

4. Use the Mole Ratio from the Balanced Equation:

The balanced equation shows that 4 moles of NH₃ react with 5 moles of O₂.

* Moles of O₂ = (11.74 mol NH₃) * (5 mol O₂ / 4 mol NH₃) = 14.68 mol O₂

5. Convert Moles of Oxygen to Grams:

* Grams of O₂ = (14.68 mol O₂) * (32.00 g/mol O₂) = 470.0 g O₂

Therefore, you need 470.0 grams of oxygen to react completely with 200.0 grams of ammonia.