Percent Yield Calculator
Calculate reaction efficiency, actual yield, or theoretical yield instantly.
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Measuring Chemical Success
In an ideal world, every atom of reactant would turn into a useful product. In the real world, spills happen, side reactions occur, and efficiency varies. Percent Yield is the chemist's report card—it grades how successfully a reaction was performed compared to the theoretical maximum.
Whether you are maximizing profit in a chemical plant or trying to pass your lab exam, knowing your percent yield is the primary metric of success.
Actual Yield
The amount you actually produce and measure on a scale at the end of the experiment. It is almost always lower than predicted.
Theoretical Yield
The maximum calculated amount possible, assuming perfect conditions and zero loss. Derived from stoichiometry.
Percent Yield
The ratio expressing efficiency.
(Actual / Theoretical) × 100%. A higher percentage equals higher efficiency.
Why is Yield Never 100%?
Sources of Loss
- 1
Mechanical Loss: Product stuck to the filter paper, beaker walls, or lost during transfer between containers.
- 2
Impure Reactants: If your starting material was only 90% pure, you can't get 100% of the predicted product.
- 3
Side Reactions: Reactants might interact in unexpected ways to form different, unwanted molecules.
Equilibrium & Kinetics
Some reactions are reversible. They naturally stop before all reactants are used up because they reach a state of equilibrium where the forward and reverse reaction rates are equal.
In these cases, getting 100% yield is physically impossible without constantly removing the product to shift the equilibrium (Le Chatelier's Principle).
Grading Your Yield
What counts as "good" depends heavily on context.
Excellent / Industrial Standard
Typical for simple reactions or highly optimized industrial processes.
Good / Lab Standard
A very respectful result for a high school or college laboratory experiment.
Average / Complex Synthesis
Common in complex organic chemistry steps where separation is difficult.
Error / Impure
Your product is likely wet or contains impurities adding false mass.
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Frequently Asked Questions
What is Percent Yield?
Percent yield is a measure of the efficiency of a chemical reaction. It tells you what percentage of the expected product you actually managed to produce. A value of 100% means perfect conversion with zero loss.
Can Percent Yield be over 100%?
Technically, no. According to the Law of Conservation of Mass, you cannot create matter. However, experimental results >100% usually mean your product is impure (contaminated with other chemicals) or simply not fully dried (contains water weight).
Why is the yield almost never 100% in real life?
Several reasons:
- Side Reactions: Reactants might form unwanted byproducts.
- Incomplete Reaction: The reaction reached equilibrium before finishing.
- Mechanical Loss: Product left on the sides of glassware or filter paper.
- Impurity: Starting materials weren't 100% pure.
What is the difference between Actual and Theoretical Yield?
Theoretical Yield is the maximum amount predicted by stoichiometry calculations (assuming perfection). Actual Yield is the amount you physically weigh on a balance after the experiment.
How do I find Theoretical Yield?
You must use stoichiometry.
- Find the Limiting Reagent.
- Convert moles of Limiting Reagent to moles of Product.
- Convert moles of Product to grams using Molar Mass.
What is a 'Good' Percent Yield?
It depends on the complexity of the reaction. In industrial preparation of something simple like Ammonia, yields can be 98%+. In complex multi-step organic synthesis (like pharmaceuticals), a yield of 70% or even 50% might be considered excellent.
How is Percent Error different from Percent Yield?
They are opposites. Percent Yield focuses on success (how much you got). Percent Error focuses on failure (how far off you were). Typically: Yield + Error ≠ 100%, because Percent Error can be calculated based on values other than 0 (e.g. overshooting).
Does temperature affect percent yield?
Yes! Changing temperature can shift the position of equilibrium (Le Chatelier's Principle), favoring either products or reactants, thus directly changing the possible yield.
What is the equation for Percent Yield?
$$ \text{Percent Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100% $$
Can I use moles instead of grams?
Yes! As long as both the Actual and Theoretical values are in the same unit (both grams, both moles, both kilograms), the ratio will be correct.