If 4.0mol of H2 react, how many moles of NH3 will be produced?

Question

Ammonia is made industrially by reacting nitrogen and hydrogen under pressure, at high temperature, and in the presence of a catalyst. The equation is N2(g)+3H2(g)————〉2NH3（g). If 4.0mol of H2 react, how many moles of NH3 will be produced?

Answer 1

Hi Kelsey!

To do this problem, we set up a proportion based on the coefficients in the provided chemical equation. According to the equation, if we put in 3 moles of H₂, we get out 2 moles of NH₃. This is true independent of how much N₂ there is. In our problem, we're putting 4 moles of H₂ in and need to know how much NH₃ we will get--let x be that amount. The proportion we set up is 3/2=4/x. The left side (3/2) expresses 3 moles H₂ in, 2 moles NH₃ out, and the right side (4/x) expresses the same order.

We solve the proportion 3/2=4/x by cross-multiplying, obtaining 3*x=4*2 or 3x=8. Divide both sides by 3 to get x=2.7 to two significant figures. So we get 2.7 moles of NH₃.

I hope this helps!