1. Percent yield is a measure of the efficiency of a chemical reaction. Section 4: Percent Yield K What I Know W What I Want to Find Out L What I Learned

2. 8(E) Perform stoichiometric calculations, including determination of mass relationships between reactants and products, calculation of limiting reagents, and percent yield. 8(A) Define and use the concept of a mole. 8(D) Use the law of conservation of mass to write and balance chemical equations. 2(G) Express and manipulate chemical quantities using scientific conventions and mathematical procedures, including dimensional analysis, scientific notation, and significant figures. Percent Yield Copyright © McGraw-Hill Education

3. Essential Questions What is the theoretical yield of a chemical reaction? How do you calculate the percent yield for a chemical reaction? Percent Yield Copyright © McGraw-Hill Education

4. Review process Percent Yield Copyright © McGraw-Hill Education Vocabulary New theoretical yield actual yield percent yield

5. How much product? Laboratory reactions do not always produce the calculated amount of products. Reactants stick to containers. Competing reactions form other products. The theoretical yield is the maximum amount of product that can be produced from a given amount of reactant. The actual yield is the amount of product actually produced when the chemical reaction is carried out in an experiment. The percent yield of a product is the ratio of the actual yield expressed as a percent. Percent Yield Copyright © McGraw-Hill Education

6. Percent Yield Copyright © McGraw-Hill Education PERCENT YIELD Use with Example Problem 6. Problem Solid silver chromate (Ag 2 CrO 4 ) forms when excess potassium chromate (K 2 CrO 4 ) is added to a solution containing 0.500 g of silver nitrate (AgNO 3 ). Determine the theoretical yield of Ag 2 CrO 4. Calculate the percent yield if the reaction yields 0.455 g of Ag 2 CrO 4. Response ANALYZE THE PROBLEM You know the mass of a reactant and the actual yield of the product. Write the balanced chemical equation, and calculate theoretical yield by converting grams of AgNO 3 to moles of AgNO 3, moles of AgNO 3 to moles of Ag 2 CrO 4, and moles of Ag 2 CrO 4 to grams of Ag 2 CrO 4. Calculate the percent yield from the actual yield and the theoretical yield. KNOWNUNKNOWN mass of silver nitrate = 0.500 g AgNO 3 theoretical yield = ? g Ag 2 CrO 4 actual yield = 0.455 g Ag 2 CrO 4 percent yield = ? % Ag 2 CrO 4

7. Percent Yield Copyright © McGraw-Hill Education PERCENT YIELD EVALUATE THE ANSWER The quantity with the fewest significant figures has three, so the percent is correctly stated with three digits. The molar mass of Ag 2 CrO 4 is about twice the molar mass of AgNO 3, and the ratio of moles of AgNO 3 to moles of Ag 2 CrO 4 in the equation is 2:1. Therefore, 0.500 g of AgNO 3 should produce about the same mass of Ag 2 CrO 4. The actual yield of Ag 2 CrO 4 is close to 0.500 g, so a percent yield of 93.2% is reasonable.

8. Percent Yield in the Marketplace Percent yield is important in the cost effectiveness of many industrial manufacturing processes. Percent Yield Copyright © McGraw-Hill Education

9. Percent Yield Copyright © McGraw-Hill Education Review Essential Questions What is the theoretical yield of a chemical reaction? How do you calculate the percent yield for a chemical reaction? Vocabulary theoretical yieldactual yieldpercent yield