 Today we are going to talk about eucalculations because a big part of chemistry is to study the properties of chemicals and chemical reactions and from that we design chemical reaction to produce the desired chemicals. For example, the ammonia production from the harbor process was one of the most well known chemical reactions. As ammonia is extremely useful and has a wide range of applications from being used to make fertilizers to making eyes and large refrigeration plans, clean products, you name it. For any chemical reaction you want to know is efficiency and you can do that by calculating the yield. So how do you calculate yield? You do that by dividing the actual yield that you collect and measure divided by the theoretical yield and by convention we multiply that number by 100% and that will give us our percentage yield, actual yield and theoretical yield can either be in mass or number of moles. So what does yield tell you? It tells you how your reaction went, whether your synthesis is efficient, whether you got the right temperature or pressure, the reaction design has too many side reaction and that. So the further you actually yield is from the theoretical yield, the smaller the percentage you and that means the less efficient your reaction was.