Percent Yield HJ Cody School百分量HJ科迪学校.pptVIP

Percent Yield Unit D: Stoichiometry Lesson 3 Theoretical vs. Actual Yields Yield: what is produced When stoichiometry is used to calculate the amount of product that will form during a chemical reaction, the theoretical yield is obtained. Theoretical yield is the maximum amount of product that could be formed from a given amount of reactant The amount of product that forms when the reaction is carried out in the laboratory is called the actual yield The actual yield is often less than the theoretical yield some reasons for this are experimental uncertainties such as All measurements Purity of chemical used Washing a precipitate Any qualitative judgments that affect measurements Calculating Percent Yield Percent yield is the ratio of the actual yield to the theoretical yield. Measures the efficiency of the reaction Percent Yield = Actual Yield x 100% Theoretical Yield *Should not be more than 100%, a percent yield over 100% violates the law of conservation of mass – “mass cannot be created or destroyed” Example Calcium Carbonate can be decomposed to calcium oxide and carbon dioxide gas by heating. What is the percent yield of this reaction if in the lab 24.8 g of CaCO3 is heated to give 13.1g of CaO? Assignment Turn to p. 291, Lab Exercise 7.A Predict the % yield of the experiment Homework Read p. 292 – 293 P. 293 # 5-8, 10 Coming up: Lab and quiz