a. We divide the grams by the weights of the molecules to get the number of oxygen and ammonia molecules. Using a periodic table, 02 weighs 2*16=32. NH3 weighs 14*3*1=42. 325/32=10.156 ; 153/42=3.642. They occur at a ratio of 5/4 in the reaction. Thus we divide accordingly: 10.156/5=2.0312 , 3.642/4=.911 . Thus ammonia is the limiting reagent. b. Thus we get .911*4 (NO) and .911*6(H20) . Including the weight of the molecules yields weights in grams. Using periodic table, we have .911*4(14+16) and .911*6(2+16). That is 109.32 and 98.388