J.R. S. answered 12/10/19
Ph.D. University Professor with 10+ years Tutoring Experience
4NH3(g) + 5O2(g) ==> 4NO(g) + 6H2O(g) ... balanced equation
You are correct that we must first find the limiting reactant.
For NH3 we have:
65.00 g NH3 x 1 mol NH3/17 g x 4 mol NO/4 mol NH3 x 30 g NO/mol = 114.7 g NO formed
For O2 we have:
150.0 O2 x 1 mol O2/32 g x 4 mol NO/5 mol O2 x 30 g NO/mol = 112.5 g NO formed <--LIMITING
Now that we have the limiting reactant (O2), and we've calculated the moles NO formed (112.5), we can convert this to molecules of NO.
112.5 g NO x 1mol/30 g = 3.75 mol x 6.02x1023 molecules/mol = 2.258x1024 molecules