Percent yield
Theoretical yield is the maximum product the equation predicts. Actual yield is what you really collect. Percent yield = (actual ÷ theoretical) × 100. It is usually less than 100 percent.
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Analogy
Baking: the recipe says 12 cookies, but you drop two and burn one, so you end up with 9.
Example
Theoretical yield = 25.0 gActual yield = 20.0 gPercent yield = 20.0 / 25.0 × 100= 80.0%
In practice
Pharmaceutical chemists try to raise percent yield because wasted starting material costs money.
Practice
Flashcards
- Formula for percent yield?(Actual yield ÷ theoretical yield) × 100.
Interview questions
- Explain how to identify the limiting reagent and why it matters.
- Convert masses to moles
- Divide by the coefficients
- The smallest result limits
- Product amount is set by the limiting reagent
Questions people ask
Why is percent yield usually below 100?
Some product stays on glassware, some reactant forms side products, and some reactions stop before all reactants are used because they reach equilibrium. Product can also be lost during purification. All these effects mean the actual mass collected is smaller than the theoretical maximum.
Can percent yield be more than 100?
If a calculation shows over 100 percent, something is wrong. The product is usually wet, impure or contaminated with solvent or leftover reactant, which adds extra mass. Drying and purifying the sample more carefully should bring the figure back below 100 percent.