Percentage yield is a concept used in chemistry which compares the theoretical yield of an experiment with the actual results observed. This is generally part of a larger problem solving process:
Step 1: Balance The Chemical Equation: Understand the nature of the reaction. What are the inputs (the reactants)? What are the products? In what ratio are the inputs converted into products?
Step 2: Identify the Limiting Reagent: The two reagents are rarely available in perfectly balanced amounts. Use the relationship identified in the chemical equation to determine which one will be the constraint.
Step 3: Calculate Theoretical Yield: How much product should the experiment have produced if the limiting reagent was totally and efficiently consumed.
Step 4: Calculate Actual Yield: Amount of product observed at the conclusion of the experiment. Should be in your lab notes.
Step 5: Percentage Yield: Ratio of Actual to Theoretical Yield.
The actual yield is often significantly lower than the theoretical yield for the reaction based on the equations. Some things that may influence this: