Identify the limiting reactant using flexible input types. See excess amounts and product yields instantly. Built for clean calculations and reliable classroom results today.
Example reaction: 2 H2 + 1 O2 -> 2 H2O. Inputs below demonstrate a typical setup.
| Species | Coeff | Basis | Amount | Molar Mass (g/mol) | Purity % |
|---|---|---|---|---|---|
| H2 | 2 | Mass | 5.00 g | 2.016 | 100 |
| O2 | 1 | Mass | 20.00 g | 31.998 | 100 |
| H2O | 2 | Product | — | 18.015 | — |
For this example, H2 typically becomes limiting when compared by n/nu.
Balanced coefficients define fixed mole ratios, so one reactant inevitably runs out first. That reactant is the limiting reagent, and it sets the reaction extent and the maximum amount of every product. The calculator identifies it by comparing each effective amount to its coefficient using a consistent, audit-friendly method.
Reactants can be entered as mass (g), direct moles (mol), solution concentration (mol/L) with volume (mL), or gas conditions (atm, L, K). Internally, volumes are converted to liters, and each input is converted to moles to enable the same limiting comparison across very different laboratory measurements.
For mass entries, moles are computed from n = m/M, where M is molar mass in g/mol. The calculator also uses molar mass to report leftover grams and product grams. As a quick check, 1.00 g of a 100 g/mol compound equals 0.0100 mol.
Solution inputs use n = C*V with V in liters, so 250 mL is treated as 0.250 L. This option is useful for titrations, buffered mixtures, and reaction screening, where the amount delivered is controlled by volumetric glassware and concentration certificates.
Gas inputs apply the ideal-gas equation n = P*V/(R*T) with R = 0.082057 L*atm*K^-1*mol^-1. Temperature must be absolute (K). At fixed pressure and volume, increasing temperature reduces moles, which can change which reactant becomes limiting in gas-phase work.
Purity scales the usable amount before comparing ratios: n_eff = n*(purity/100). A 95% pure reagent contributes only 0.95 of the moles you calculated from label mass or solution preparation. This adjustment helps explain unexpected shortfalls and supports more realistic yield predictions.
The extent xi is the smallest value of n_eff/nu. Once xi is known, consumed reactant moles are nu*xi, and remaining moles are n_eff - nu*xi. The accounting table is an immediate consistency check for planned mixtures and scaled batches.
Product moles follow n_product = nu_product*xi, and theoretical grams follow moles times molar mass. If you enter an actual isolated mass, percent yield is calculated as actual/theoretical*100. Exporting CSV supports spreadsheets and lab notebooks, while PDF provides a compact report for sharing and reproducibility.
It is effective moles divided by the stoichiometric coefficient. The smallest ratio indicates the reactant that runs out first and limits the reaction.
Molar mass is required for mass-based inputs and for gram-based leftovers. If you enter moles directly, molar mass is optional unless you want product masses.
Purity reduces the usable amount before the limiting comparison. A lower purity can change which reactant is limiting and will lower theoretical yield.
Yes. Enable Reactant C and Reactant D, then enter coefficients and amounts. The calculator compares all active reactants and picks the smallest effective ratio.
The ideal-gas equation uses absolute temperature. Convert Celsius to kelvin by adding 273.15 before entering values for accurate moles.
Provide product molar mass to compute theoretical grams from nu*xi. Percent yield equals actual grams divided by theoretical grams, multiplied by 100.
Coefficients set the reaction ratios, so an unbalanced equation gives incorrect limiting and yield results. Balance the equation first, then enter integer coefficients.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.