Percent Yield Sometimes all the product in a

Percent Yield Sometimes all the product in a chemical reaction is not produced. Some of the reactant might produce other products or some of the reactants might be spilled when transferred from the balance to the test tube or beaker.

Chemists are interested in the efficiency of the reaction. The efficiency is measured by comparing the actual yield to theoretical yield.

Actual yield = the amount of product produced by actually performing the reaction in lab and measuring its mass. Theoretical yield = the amount of product that should be produced based on a stoichiometry calculation.

Stoichiometry Problem Zn + 2 HCl a Zn. Cl 2 + H 2 A lab group dropped 6. 5 g of zinc into a test tube containing hydrochloric acid (HCl). After the reaction was over they measured 12 g of Zn. Cl 2 produced by this reaction. What is theoretical yield? What is the percent yield?

Stoichiometry Problem Zn + 2 HCl a Zn. Cl 2 + H 2 6. 5 g 12 g What is theoretical yield? 1 mol Zn 136 g Zn. Cl 2 1 mol Zn. Cl 6. 5 g Zn x ______ 2 ____________ x x = 13. 6 g Zn. Cl 2 65 g Zn 1 mol Zn. Cl 2 1 mol Zn

Stoichiometry Problem Zn + 2 HCl a Zn. Cl 2 + H 2 6. 5 g Zn x 12 g = actual yield 13. 6 = theoretical yield 1 mol Zn. Cl 2 ______ x 1______ 65 g Zn 1 mol Zn x 136 g Zn. Cl ______2 = 13. 6 1 mol Zn. Cl 2 g Zn. Cl 2

Stoichiometry Problem Zn + 2 HCl a Zn. Cl 2 + H 2 6. 5 g 12 g = actual yield 13. 6 g = theoretical yield What is the percent yield? 12 g % yield = 13. 6 g X 100 = 88 %

Another lab group burned 3. 0 g of magnesium and collected 4. 2 g of Mg. O. What is their percent yield? 2 Mg + O 2 3. 0 g a 2 Mg. O 4. 2 g % yield = X 100 theoretical yield

2 Mg + O 2 3. 0 g 0. 125 mole a 2 Mg. O 4. 2 g = actual yield 0. 125 5. 0 g =mole theoretical yield Theoretical yield: 1 mol Mg 2 mol Mg. O 40 g Mg. O 3. 0 g Mg x ____________ x x = 5. 0 g Mg. O 24 g Mg 1 mol Mg. O 2 mol Mg actual yield 4. 2 g % yield = X 100 = 84 % theoretical 5. 0 g yield