Percent yield — Science definition
The actual yield expressed as a percentage of the theoretical yield: (actual ÷ theoretical) × 100%.
Where it is taught
- Limiting Reactants & Percent Yield — Stoichiometry & Yield, Physical Science: Chemistry, Grade 11
In use
To measure how well a reaction performed, chemists compare the two with the percent yield: actual yield divided by theoretical yield, times 100%.
Limiting Reactants & Percent Yield
Questions using percent yield
Problem 1
A reaction has a theoretical yield of 50.0 g but an actual yield of 45.0 g. What is the percent yield?
Answer and explanation
90 %
percent yield = (45.0 ÷ 50.0) × 100% = 90%.
Problem 2
A student predicts a theoretical yield of 25.0 g but isolates only 20.0 g of product. What is the percent yield?
Answer and explanation
80 %
percent yield = (20.0 ÷ 25.0) × 100% = 80%.
Problem 3
Theoretical yield is 25 g and actual isolated yield is 20 g. Find percent yield. Show the reasoning, not just the conclusion.
Hints
Compare required ratios, not just smaller starting mole count.
Answer and explanation
20/25×100%=80%.
Problem 4
A reaction has a theoretical yield of 20.0 g and an actual yield of 18.0 g. What is the percent yield?
Answer and explanation
90 %
percent yield = (18.0 ÷ 20.0) × 100% = 90%.