Ammonia and oxygen react to form nitrogen and water.

4NH3(g)+3 O2(g)-2N2(g)+6H2O(g)

a.How many grams of O2 are needed to react with 8.00 mol NH3?

8.00 mol NH3 x42.094/4 mol NH3 x32.00 O2/1 mol O2=269gO2

2 answers

I don't know where the 42.094 came from.

8.00 mole NH3.
Convert to moles oxygen.
8 x (3 moles O2/4 moles NH3) = 6.00 moles oxygen.

Now convert 6.00 moles oxygen to grams. g = moles x molar mass.
96 gm.