11-3 Limiting Reactants

1. 11-3 Limiting Reactants Reactions to this point have had one ingredient in excess. When you are given two or both reactant amounts, you have a limiting reagent problem. A limiting reagent is one that runs out to stop a reaction. An excess reagent is one that has extra left over when the other reagent runs out. To solve these problems, solve both reactants for one of the products…the one that makes the least is the limiting reagent.

2. 11-3 Limiting Reactants • 2H2 + O2 2H2O • Given the above reaction, when 6.0 moles of H2 react with 2.8 moles of oxygen, … • A)What is the limiting reactant. • B)How much product is formed? • C)How much excess reagent is left after the reaction?

3. 11-4 Percent Yield • The percent yield formula is… • %Y= actual yield x 100 theoretical yield *The actual yield is the amount actually produced, in the lab. *The theoretical yield is your calculated value for what product should have been made. *To solve these…. 1)write the formula %Y=A/T x 100 2)Plug in the actual yield from the problem. 3)Solve for the theoretical yield and plug it in. 4)Solve for %Y

4. % Yield • Try this problem… • Problem: What is the percent yield of the following reaction if 60.0 grams of CaCO3 is heated to give 15.0 grams of CaO? • CaCO3→CaO + CO2 • Solution…Plug in the 15.0 grams for the actual yield. • Solve for grams of CaO using 60.0 grams CaCO3… • Plug that result into the theoretical yield. • 60.0grams CaCO3 x 56.1 g CaO = 33.6 g CaO • 1 100.1 g CaCO3 = 0.446 = 44.6%