How do I solve for mass of Ammonia while taking in consideration both reactants at the same time?

Question

The chemical reaction that produces ammonia is known as the Haber process. What mass of ammonia can be produced from the reaction of 7.00 g of hydrogen gas reacting with 10.0 g of nitrogen gas?

         ___H2 + _____N2 ---> _____NH3

Answer 1

Whenever you are given the mass or moles of BOTH (or more) reactants, you MUST determine which reactant is limiting (if any). That is, which reactant will run out before the others. One easy way to do this is to simply divide the moles of each reactant by the corresponding coefficient in the balanced equation. So, that means we first need a balanced equation.

3H₂ + N₂ ==> 2NH₃ .. balanced equation

For H₂: 7.00 g H₂ x 1 mol H₂ / 2 g = 3.5 mols H₂ (÷3->1.17)

For N₂: 10.0 g N₂ x 1 mol N₂ / 28 g = 0.357 mos N₂ (÷1->0.357)

Since 0.357 is less than 1.17, N₂ is the limiting reactant and mols of N₂ will determine amount NH₃ formed.

Mass NH₃ formed = 0.357 mols N₂ x 2 mols NH₃ / 1 mol N₂ x 17 g NH₃ / mol NH₃ = 12.1 g NH₃