chemistry problem

Question

1.28g H2 is allowed to react with 10.5g N2 , producing 2.96g NH3?

What is the theoretical yield for this reaction under the given conditions? and What is the percent yield for this reaction under the given conditions?

how do I solve this problem I'm stuck

Answer 1

Write the balanced equation for the reaction taking place:

3H₂ + N₂ ==> 2NH₃

Next, find which reactant is limiting:

mols H₂ = 1.28 g H₂ x 1 mol H₂ / 2 g = 0.64 mols H₂

mols N₂ = 10.5 g N₂ x 1 mol N₂ / 28 g = 0.375 mols N₂

Because it takes THREE mols H₂ for every ONE mol N₂ (see balanced equation), the H₂ is LIMITING

Theoretical yield:

Theoretical yield is determined by the moles of limiting reactant.

0.64 mols H₂ x 2 mols NH₃ / 3 mols H₂ x 17 g / mol NH₃ = 7.25 g NH₃

% yield = actual yield / theoretical yield (x100%):

2.96 g / 7.25 g (x100%) = 40.8% yield