Question

N2 (g) + 3H2 (g) -->2 NH3 (g)

Answer 1

Answer: 6 mol NH3.

Explanation:

1) You have to work with the balanced chemical equation, which is given:

N2(g) + 3H2 (g) → 2 NH3 (g)

2) The mole ratios are:

1 mol N2 : 3 mol H2 : 2 mol NH3

3) Determine wich reactant is limiting the reaction

3.0 moles N2
------------------- = 0.75
4.0 moles H2

Theoretical ratio:

1 mol N2
------------ = 0.33
3 mol H2

0.33 < 0.75 means that there is less N2 than the theoretically needed to react with 4 moles of H2, so N2 is the limiting reactant.

Therefore, the 3.0 moles of N2 will react fully and you can set the proportion with that to find the amount of  NH3 produced.

4) Set the proportion

2 mol NH3           x
----------------- =  --------
1 mol N2            3 mol N2

5) Solve for x:

x = 3 mol N2 * 2 mol NH3 / 1 mol N2 = 6 mol NH3

Answer: 6 mol NH3.

That is the double number of moles than the moles of N2 that react, which is what the balanced chemical equation given.