Enter reaction data
Provide coefficients and molar masses. For reactants, provide an amount in grams or moles.
Example data table
Example: 2 H2 + 1 O2 → 2 H2O
| Species | Role | Coefficient | Molar mass (g/mol) | Amount provided |
|---|---|---|---|---|
| H2 | Reactant | 2 | 2.016 | 5.00 g |
| O2 | Reactant | 1 | 31.998 | 10.00 g |
| H2O | Product | 2 | 18.015 | Target product |
Try entering these values to see limiting reagent and theoretical yield.
Formula used
1) Convert masses to moles
n = m / M
Where n is moles, m is mass (g), and M is molar mass (g/mol).
2) Find the limiting reagent
Compare (ni / ai) for each reactant
The smallest value determines the limiting reagent. Here ai is the reactant coefficient.
3) Reaction extent and theoretical yield
xi = nlim / alim
nproduct = xi × c
mproduct = nproduct × Mproduct
Where c is the product coefficient.
4) Percent yield (optional)
% yield = (actual / theoretical) × 100
How to use this calculator
- Enter each reactant’s name, coefficient, molar mass, and amount.
- Choose grams or moles for each reactant amount.
- Enter product coefficients and molar masses for products you care about.
- Select a target product for theoretical and percent-yield reporting.
- Optionally enter an actual yield to compute percent yield.
- Press Calculate to show results above the form.
- Use the download buttons to export CSV or PDF.
Tip: Use a balanced reaction. Coefficients must match the balanced equation.
Professional guide to stoichiometry results
1) Why stoichiometry matters in physics workflows
Stoichiometry connects particle counts to measurable mass, so it appears in combustion, plasma chemistry, propellant design, corrosion, battery reactions, and atmospheric kinetics. In experimental physics, accurate reactant ratios reduce waste heat, control by‑products, and stabilize repeatable conditions. In high-rate systems, stoichiometric mismatch can shift energy release and gas production, altering pressure transients. For beams or detectors in reactive environments, predicting residual reactants helps estimate contamination, optical absorption, and component lifetime during long experimental campaigns.
2) Coefficients represent conservation constraints
A balanced equation encodes conservation of atoms and, indirectly, charge. The calculator treats coefficients as fixed constraints, so changing any coefficient changes all predicted amounts. If the equation is not balanced, the limiting reagent and yield outputs become physically inconsistent.
3) Limiting reagent defines the reaction extent
For each reactant, the tool compares available moles divided by its coefficient. The smallest ratio identifies the limiting reagent and sets the reaction extent ξ. This mirrors a constrained resource problem: once the limiting reagent is consumed, progress stops even if others remain.
4) Converting grams to moles is the critical bridge
When you enter grams, the calculator uses n = m/M. Accurate molar masses matter: a 1% molar‑mass error produces about a 1% error in computed moles, propagating into ξ, theoretical yield, and remaining excess estimates.
5) Theoretical yield and percent yield
Theoretical yield follows from nproduct = ξ·c and mproduct = n·M. If you provide an actual yield, percent yield compares actual to theoretical. Values over 100% usually indicate impurities, wet samples, unit mistakes, or measurement bias.
6) Multiple products and choosing a target
Real reactions may form several products. Selecting a target product focuses reporting on the output you care about, while the table still predicts all entered products. This is useful for optimizing desired yield while tracking side‑product formation.
7) Uncertainty, significant figures, and rounding
Stoichiometry is sensitive to input precision. Use consistent significant figures: masses from balances, volumes from glassware, and molar masses from reliable references. After calculation, round results to match the least precise measured input to avoid overstating certainty.
8) Good reporting and export practices
Record the balanced equation, input amounts, limiting reagent, ξ, theoretical yield, and percent yield. Export CSV for lab notebooks or scripts, and PDF for sharing in reports. Always note temperature, pressure, and purity when comparing runs across setups.
FAQs
1) Do I need a balanced equation first?
Yes. Coefficients must come from a balanced reaction. If they are not balanced, conservation rules are violated and the limiting reagent and yield predictions will not represent a physical reaction.
2) Can I mix grams and moles for reactants?
Yes. Choose grams or moles for each reactant. The calculator converts grams to moles using the molar mass, then applies the coefficient ratios to determine the limiting reagent and yields.
3) What does “reaction extent” mean here?
Reaction extent ξ is the scaling factor for the balanced equation. Multiply ξ by any coefficient to get moles consumed or produced. It is set by the limiting reagent’s available moles divided by its coefficient.
4) Why is my percent yield above 100%?
Common causes are wet or impure product, incomplete drying, side reactions that add mass, incorrect molar mass, or unit entry mistakes. Recheck inputs and measurement conditions before interpreting the result.
5) How many reactants and products can I enter?
You can enter up to three reactants and three products. Leave unused rows blank. The target product selector chooses which product is used for theoretical and percent-yield reporting.
6) What if a reactant is in large excess?
The limiting reagent logic will identify another reactant as limiting. Excess reactants show positive remaining moles and grams in the reactant summary table, helping you estimate leftovers for recovery or disposal planning.
7) How should I round results for reporting?
Round to match your least precise measured input. Keep extra digits during intermediate steps, then report final moles and masses with appropriate significant figures. Document temperature, pressure, and purity when comparing runs.