The first step in the Ostwald process used to produce nitric acid is the formation of nitric oxide from ammonia and oxygen.
4 NH3 (g) + 5 O2 (g) -------> 4 NO (g) + 6 H20 (g)
If the feed going to the reactor contains 0.250 mol NH3/mol O2, what is the limiting reactant, and the percent excess of the other reactant?