Percent yield measures the efficiency of a chemical reaction by comparing the actual amount of product obtained to the theoretical maximum possible. It's essential for evaluating reaction success in labs and industry.
% Yield = (Actual / Theoretical) × 100
Efficiency of a chemical reaction
Units: % (percentage)
Range: 0% to ~100% (over 100% indicates experimental error)
Meaning: Efficiency of the reaction
Units: g, kg, mol (must match theoretical yield units)
Meaning: Amount of product actually obtained from experiment
📊 Measured in the lab
Units: g, kg, mol (must match actual yield units)
Meaning: Maximum amount of product possible based on stoichiometry
🧮 Calculated from balanced equation and limiting reactant
Actual = (% Yield × Theoretical) / 100
Predict actual product amount
Theoretical = (Actual × 100) / % Yield
Calculate theoretical from actual
% Yield = (Actual / Theoretical) × 100
% Yield = (42.3 g / 50.0 g) × 100
% Yield = 0.846 × 100 = 84.6%
Answer: 84.6% — This is a good yield for most reactions!
Many reactions don't go to 100% completion. Equilibrium may favor reactants.
Competing reactions may form unwanted products, reducing main product yield.
Some product sticks to glassware, is lost during transfer, or evaporates.
Impure products must be purified, which reduces the final amount recovered.
Actual (what you got) goes in the numerator. Theoretical (calculated maximum) goes in denominator.
Both yields must be in the same units! Can't divide grams by moles.
0.846 is NOT the percent yield. Multiply by 100 to get 84.6%.
If you get over 100%, you likely have impure product, measurement error, or wrong theoretical yield calculation.
% Yield = (Actual Yield / Theoretical Yield) × 100. It measures reaction efficiency as a percentage.
80-90% is excellent. 70-80% is good. Below 50% suggests problems. Industrial processes aim for over 90%.
No! Over 100% indicates error: impure product, wet product, wrong theoretical calculation, or measurement mistakes.
Use stoichiometry: Find limiting reactant, convert to moles, use mole ratio from balanced equation, convert to desired units.
Theoretical = calculated maximum from stoichiometry. Actual = what you actually got in the lab. Actual is usually less.