The balanced reaction is:
N2+3H2→2NH3\text{N}_2+3\text{H}_2\rightarrow 2\text{NH}_3N2​+3H2​→2NH3​.

From this, the mole ratio is:

  • 333 moles H2\text{H}_2H2​ : 222 moles NH3\text{NH}_3NH3​.

To find the moles of H2\text{H}_2H2​ needed for 30.030.030.0 moles NH3\text{NH}_3NH3​:

moles H2=30.0×32=45.0 moles\text{moles }\text{H}_2=30.0\times \frac{3}{2}=45.0\text{ moles}moles H2​=30.0×23​=45.0 moles

So, 45.0 moles of H₂ are theoretically needed to produce 30.0 moles of NH₃.