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Unformatted text preview: Anna ToyPalmer 1 Chem 100 Ch 8  Limiting Reactant, Theoretical Yield and Percent Yield Suppose in a pancake recipe, 1 cup of pancake mix plus 1 cup of water makes 8 pancakes. Stoichiometric amounts means that all reactants are in amounts exactly required by the recipe. In this case, stoichiometric amounts would be 1 cup of pancake mix and 1 cup of water (or 2 cups mix and 2 cups water, etc). If we do not have stoichiometric amounts of each reactant, then we need to determine the limiting reactant and theoretical yield. Anna ToyPalmer 2 Chem 100 Ch 8  Limiting Reactant, Theoretical Yield and Percent Yield Suppose in a pancake recipe, 1 cup of pancake mix plus 1 cup of water makes 8 pancakes. The reactant that limits how much product can be made is called the limiting reactant . Suppose we had ½ cup of pancake mix and 1 cup of water. How many pancakes would we make? So what is our limiting reactant? Anna ToyPalmer 3 Chem 100 Ch 8  Theoretical Yield The theoretical yield is the amount of product that can be made based on the amount of limiting reactant. Suppose we had ½ cup of pancake mix and 1 cup of water. How many pancakes would we make? Therefore, what is our theoretical yield? Anna ToyPalmer 4 Chem 100 Ch 8  Percent Yield The actual yield (amount of product actually made) divided by the theoretical yield times 100%. Yield Percent 100% X Yield l Theoretica Yield Actual = Anna ToyPalmer 5 Chem 100 Ch 8  Percent Yield Suppose we had ½ cup of pancake mix and 1 cup of water. We make the 4 pancakes but 1 is accidentally dropped on the floor and 1 is burnt. Therefore, only 2 pancakes can be served at breakfast. What is our actual yield? 50% 100% X pancakes 4 pancakes 2 Yield Percent 100% X Yield l Theoretica Yield Actual = = Anna ToyPalmer 6 Chem 100 Stoichiometric amounts : amounts in the proportions determined by the chemical equaiton Limiting Reactant : the reactant that produces the least amount of product Theoretical Yield : the theoretical amount of product based on the limiting reactant Actual yield : the actual amount produced (this must be given as the value is an experimental value) Percent Yield : 100% X Yield l Theoretica Yield Actual Anna ToyPalmer 7 Chem 100 Given the reaction: 2 Al(s) + 3 Cl 2 (g) 2 AlCl 3 (s) Given: 0.552 mol Al 0.887 mol Cl 2 Find: limiting reactant theoretical yield Anna ToyPalmer 8 Chem 100 2 Al(s) + 3 Cl 2 (g) 2 AlCl 3 (s) Given: 0.552 mol Al 0.887 mol Cl 2 Find: limiting reactant theoretical yield Conversion factors: 2 Al Ξ 2 AlCl 3 , 3 Cl 2 Ξ 2 AlCl 3 Anna ToyPalmer 9 Chem 100 Now we determine how many moles of AlCl 3 we can obtain if Al were the limiting reactant or if Cl 2 were the limiting reactant....
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This note was uploaded on 02/05/2011 for the course CHE M 100 taught by Professor Palmer during the Spring '09 term at CSU Northridge.
 Spring '09
 Palmer

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