How many grams of nitrogen are needed to produce 21.8 grams of ammonia? N2 + 3 H2 → 2 NH3

Answer 1

First, you want to check and make sure that your equation is balanced (it is). For this problem, you're going to work "backwards" from the product.

A few things you'll need for this problem:

1. The molar mass of ammonia is 17.03 g/mol
2. The molar mass of N₂ is 28.013 g/mol

Starting from grams of ammonia...

21.8 grams NH₃ × (1 mol NH₃ / 17.03 grams) = 1.28 moles of NH₃

Now that you have the moles of NH₃, you can convert to moles of Nitrogen needed by using the molar ratio from the balanced equation.

1.28 moles NH₃ × ( 1 mol N₂ / 2 mols NH₃) = 0.64 moles of N₂

Now that you have moles of N₂, you can convert this into grams of N₂.

0.64 moles N₂ × (28.013 grams N₂ / mol N₂) = 17.93 grams of N₂ needed



Once you become more familiar with this type of problem you'll be able to do it all in one equation:

21.8g NH₃ × (1 mol NH₃ / 17.03g NH₃)× ( 1 mol N₂ / 2 mol NH₃) × (28.013g N₂ / mol N₂) = 17.93g N₂