NIS – CHEMISTRY

1. NIS – CHEMISTRY Lecture 65 Percent Yield OzgurUnal

2. Percent Yield • 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. When you pop a bag of popcorn, do all of the popcorns pop inside the bag?

3. Percent Yield • 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 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.

4. Percent Yield Example: Solid silver chromate (Ag2CrO4) forms when potassium chromate (K2CrO4) is added to a solution containing 0.500 g of silver nitrate. Determine the theoretical yield of Ag2CrO4. Calculate the percent yield if the reaction yields 0.455 g of Ag2CrO4. • Example:Zinc reacts with iodine in a synthesis reaction. Determine the theoretical yield if 1.912 mol of zinc is used.Determine the percent yield if 515.6 g of product is recovered.