Question

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

The equation above is the equation for the Haber process.

In a certain reaction, you start with 3.0 moles of nitrogen and 5.0 moles of hydrogen, which is the excess reactant?

Answer 1

The nitrogen is in excess. You need 3 moles of H2 for every mole of N2 you use. 3.0 mol N2 would need 9.0 mol H2, with only 5.0 mol H2 you'll only use up a little less than 2 mol N2.