1. Limiting Reagent and Percent Yield
Chemistry
Limiting Reagent and Percent Yield

2. Limiting and Excess Reagents
An insufficient quantity of any of the reactants will limit the amount of product that forms. Limiting reagent – the reagent that determines the amount of product that can be formed. Excess reagent – the reagent that is not completely used up.

3. Determining the Limiting Reagent
For the equation 2Cu(s) + S(s) → Cu2S(s) What is the limiting reagent when 80.0g Cu reacts with 25.0g S? Knowns: Cu = 80g S = 25.0g

4. 80. 0g Cu x g Cu2S = 100 g Cu2S 128g Cu 160 g Cu2S 25
80.0g Cu x g Cu2S = 100 g Cu2S 128g Cu 160 g Cu2S 25.0g S x g Cu2S = 125 g Cu2S 32 g S 160 g Cu2S With the amounts you have, you can make more Cu2S with the sulfur, so Cu is the limiting reagent.

5. Using Limiting Reagent to Find Quantity of a Product
For 2Cu(s) + S(s) → Cu2S(s)
What is the maximum number of grams of Cu2S that can be formed when 80.0 g Cu reacts with 25.0g S?
Previously determined that Cu is the limiting reagent.
Solve for g Cu2S using only the Cu information.

6. Percent Yield
Theoretical yield – the maximum amount of product that will form during a reaction. Actual yield – the amount of product that actually forms. Percent yield – ratio of actual to theoretical yield. Percent yield = actual yield X 100 theoretical yield

7. Calculating Theoretical Yield
For CaCO2(s) → CaO(s) + CO2(g)
What is the theoretical yield of CaO if 24.8g CaCO2 is heated?
Knowns: CaCO2 = g/mol
CaO = 56.1 g/mol
24.8 g CaCO x g CaO = 13.9g CaO
100.1g CaCO g CaO

8. Calculating Percent Yield of a Reaction
What is the percent yield if 13.1g CaO is actually produced when 24.8g CaCo3 is heated? Knowns: actual yield =13.1g CaO theoretical yield = 13.9g CaO 13.1g CaO X 100 = 94.2% 13.8g CaO

9. Homework - Worksheet