Stoichiometry: Other Units

Question

N2+3H2---> 2NH3

If we wish to make 20L NH3 How many grams N2 should we use at STP?

Answer 1

At STP, 1 mole of any ideal gas = 22.4 L

First, we'll find the mols of NH₃ and then find the moles of N₂ and finally the grams of N₂.

20 L NH₃ x 1 mol NH₃ / 22.4 L = 0.893 moles NH₃

From the balanced equation, we can now find the moles of N₂ needed:

0.893 mols NH₃ x 1 mol N₂ / 2 mols NH₃ = 0.447 mols N₂ needed

Now we convert this to grams of N₂ using the molar mass of N₂ of 28 g/mol:

0.447 mols N₂ x 28 g / mol = 12.5 g N₂