1. Chapter 9, section 3, part 2 Percent Yield

2. Why percent yield?  Usually, not all the product possible is actually formed.  theoretical yield  maximum amount of product possible  is calculated using limiting reactant and stoichiometry  actual yield  the measured amount formed in lab reaction  always less than or equal to theoretical yield

3. Example 1  If 72.0 g of C 2 H 2 reacts with an excess of Br 2 and 729 g of the product is recovered, what is the percent yield? C 2 H 2 + Br 2  CHBr 2 CHBr 2 First calculate theoretical yield: 72.0 g C 2 H 2 1 mol C 2 H 2 1mol CHBr 2 CHBr 2 345.64 g CHBr 2 CHBr 2 26.04 g C 2 H 2 1 mol C 2 H 2 1 mol CHBr 2 CHBr 2 26.04 g C 2 H 2 1 mol C 2 H 2 1 mol CHBr 2 CHBr 2 = 956 g CHBr 2 CHBr 2 Then calculate percent yield: 729 g 100% = 76.3% 956 g

4. Example 2  If the percent yield of the reaction below is 73.8% and the reaction began with 24.3 g of CaO, how many grams of Ca(OH) 2 were created? CaO + H 2 O  Ca(OH) 2 First, calculate theoretical yield: 24.3 g CaO 1 mol CaO 1 mol Ca(OH) 2 74.09 g Ca(OH) 2 = 32.1 g Ca(OH) 2 56.07 g CaO 1 mol CaO 1 mol Ca(OH) 2 56.07 g CaO 1 mol CaO 1 mol Ca(OH) 2 Then use given percent yield to calculate actual yield: 32.1 g Ca(OH) 2 x 0.738 = 23.7 g Ca(OH) 2