How this calculation works
The Percent Yield & Reaction Efficiency Calculator computes the synthetic efficiency percentage of chemical reactions by comparing actual experimentally recovered mass to theoretical maximum stoichiometric yield.
Mathematical formula and logic
Percent Yield (%) = (Actual Yield / Theoretical Yield) × 100. Mass Lost = Theoretical Yield - Actual Yield.
Worked example
Synthesizing Aspirin where stoichiometric calculations predict a theoretical yield of 17.5 grams, and the actual recovered purified mass is 14.2 grams: Percent Yield is (14.2 / 17.5) × 100 = 81.14% (3.30g lost).
Calculation assumptions
- Actual yield represents purified, dried chemical product.
- Theoretical yield is calculated based on 100% conversion of the limiting reactant.
Frequently asked questions
What is theoretical yield?
Theoretical yield is the maximum amount of product that could be formed from given quantities of reactants assuming 100% complete conversion without side reactions or material loss.
Why is actual yield almost always less than 100%?
Common reasons include incomplete equilibrium reactions, competing side reactions producing by-products, mechanical losses during filtration/transfer, and purification losses during recrystallization.
Can percent yield exceed 100%?
A calculated percent yield above 100% indicates experimental error—most commonly wet un-dried product retaining residual solvent/water, or unseparated impurities.
What is considered a good percent yield in organic synthesis?
In organic chemistry laboratories, yields above 80% are considered very good; yields between 50% and 80% are common for multi-step syntheses.
What is a limiting reactant?
The limiting reactant (limiting reagent) is the substance that is totally consumed first during a chemical reaction, which dictates the theoretical maximum yield of product.
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