Theoretical yield and limiting reagent
Enter the balanced equation's reactants and masses; get the limiting reagent and the theoretical yield.
Work it out
The equation must already be balanced — the coefficients are what make the answer mean anything.
11.1486 g
Limiting reagent: benzoic acid · 0.0818847 mol of product
- benzoic acid: 0.0818847 mol, divided by its coefficient gives 0.0818847.
- methanol: 0.468136 mol, divided by its coefficient gives 0.468136.
- The smallest of those is benzoic acid, so it runs out first and limits the reaction.
- Product: 0.0818847 × 1 = 0.0818847 mol, which is 11.1486 g.
A worked example
10.0 g of benzoic acid (C₇H₆O₂) and 15.0 g of methanol (CH₄O), making methyl benzoate (C₈H₈O₂), all coefficients 1.
Benzoic acid is limiting; 11.1 g of methyl benzoate
- 1Benzoic acid: 10.0 / 122.12 = 0.0819 mol; divided by its coefficient of 1 gives 0.0819.
- 2Methanol: 15.0 / 32.04 = 0.468 mol; divided by 1 gives 0.468.
- 30.0819 is the smaller, so benzoic acid runs out first and limits the reaction.
- 4Product: 0.0819 mol × 136.15 g/mol = 11.1 g.
What this assumes
- The equation must already be balanced — the coefficients are what make this calculation mean anything, and nothing here checks them for you.
- This is the ceiling, not a prediction. It assumes every molecule of the limiting reagent becomes the product you asked about, with nothing lost to side reactions or work-up.
The terms used here
- Limiting reagent
- The reactant that runs out first. It is the one with the least moles per unit of reaction, which is not always the one with the fewest moles.
- Excess reagent
- Everything else. Some is left over when the reaction stops.
- Stoichiometric coefficient
- The number in front of a species in the balanced equation.
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