NIS – CHEMISTRY Lecture 65 Percent Yield Ozgur Unal 1

Percent Yield  When you pop a bag of popcorn, do all of the popcorns pop inside the bag? 2  Some popcorns remain unpopped....  Similarly, in a chemical reaction, not all the reactants react to produce a product.  There can be several reasons for this:  Liquid reactants might adhere to the surfaces of their containers or evaporate.  Products other than intended ones might be formed bu competing reactions  These factors reduce the yield of the desired product.

Percent Yield  In our previous calculations, we determined the amounts of the products formed in chemical reactions  Theoretical yield  A reaction rarely produces the theoretical yield of product.  The actual yield is the amount of product produced when the chemical reaction is carried out in an experiment. 3  Chemists need to know how efficient a reaction is in producing the desired product.  One way of measuring efficiency is by means of percent yield.  Percent yield of product is the ratio of the actual yield to the theoretical yield expressed as a percent percent yield = 100 * actual yield / theoretical yield

Percent Yield  Example: Solid silver chromate (Ag2CrO4) forms when potassium chromate (K2CrO4) is added to a solution containing g of silver nitrate. Determine the theoretical yield of Ag2CrO4. Calculate the percent yield if the reaction yields g of Ag2CrO4. 4  Example: Zinc reacts with iodine in a synthesis reaction. Determine the theoretical yield if mol of zinc is used. Determine the percent yield if g of product is recovered.