Reactions in Practice Theoretical, Actual, and Percent Yields

Chemical Reactions in Practice Theoretical, Actual, and Percent Yields 

Up until now, we ve been optimistic about the amount of product obtained from a reaction. We have assumed that 100% of the limiting reactant becomes product, that ideal separation and purification methods exist for isolating the product, and that we use perfect lab technique to collect all the product formed. In other words, we have assumed that we obtain the theoretical yield, the amount indicated by the stoichiometrically equivalent molar ratio in the balanced equation. 

This reaction decreases the amounts of reactants available for N2 production (see Problem 3.81 at the end of the chapter). Even more important, as we ll discuss in later chapters, many reactions seem to stop before they are complete, which leaves some limiting reactant unused. But, even when a reaction does go completely to product, losses occur in virtually every step of the separation procedure used to isolate the product from the reaction mixture. With careful technique, you can minimize these losses but never eliminate them. 

The amount of product that you actually obtain is the actual yield. Theoretical and actual yields are expressed in units of amount (moles) or mass (grams). 

The percent yield (% yield) is the actual yield expressed as a percentage of the theoretical yield  

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