1. Write the balanced chemical equation:

N₂ (g) + 3H₂ (g) → 2NH₃ (g)

This equation tells us that 3 moles of hydrogen gas (H₂) are needed to react with 1 mole of nitrogen gas (N₂) to produce 2 moles of ammonia (NH₃).

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

* Nitrogen (N) has a molar mass of 14.01 g/mol

* Hydrogen (H) has a molar mass of 1.01 g/mol

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

3. Convert grams of ammonia to moles:

* Moles of NH₃ = (170000 g NH₃) / (17.04 g/mol NH₃) = 9976.53 mol NH₃

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

* From the equation, 3 moles of H₂ produce 2 moles of NH₃.

* Moles of H₂ = (9976.53 mol NH₃) * (3 mol H₂ / 2 mol NH₃) = 14964.80 mol H₂

Therefore, you need approximately 14964.80 moles of hydrogen to make 170000 g of ammonia.