Calculator
Theoretical Yield Calculator
The maximum mass of product a reaction can give — from the limiting reactant and the balanced equation.
Experiment
Printed on the lab result card.
Reactant and product
Enter the limiting reactant — the one that runs out first.
As weighed.
From the balanced equation.
From the balanced equation.
Try a worked example
Laboratory calculation card
Enter the mass, both molecular weights and the coefficients.
Moles = Mass / Molecular weight
Product moles = Reactant moles × (Product coefficient / Reactant coefficient)
Theoretical yield = Product moles × Product molecular weight
With several reactants, divide each reactant's moles by its coefficient. The smallest quotient is the reaction extent ξ — the number of “reaction units” that can actually happen — and belongs to the limiting reactant. Every product forms as ξ × its coefficient; every other reactant is left over by its moles − ξ × its coefficient.
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References
- Furniss BS, Hannaford AJ, Smith PWG, Tatchell AR. Vogel's Textbook of Practical Organic Chemistry. 5th ed. Harlow: Longman Scientific & Technical; 1989.
Common questions
Because reactions consume moles in the ratio of the balanced equation, not grams. A heavy molecule gives few moles per gram, and a coefficient of 2 means that reactant is used twice as fast. Only moles ÷ coefficient compares reactants fairly.
Convert the volume to mass first: mass (g) = volume (mL) × density (g/mL). For acetic anhydride, 5.0 mL × 1.08 g/mL = 5.4 g. Then enter the mass with its molecular weight.
The one for the material you weighed. Magnesium chloride hexahydrate (MgCl₂·6H₂O, about 203.3 g/mol) gives far fewer moles per gram than anhydrous MgCl₂ (about 95.2 g/mol). Using the wrong one is the commonest source of an impossible percentage yield.
Not in reality, but it often does on paper: a product that is still wet, contains solvent, or is contaminated with an excess reagent weighs more than pure product. Treat a result above 100% as a sign to dry, purify or re-weigh.
Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy