Limiting Reagent Calculator

ANA›Life Services Authority›National Calculator Authority›Limiting Reagent Calculator

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Limiting Reagent Calculator

Determine the limiting reagent, excess reagent, and theoretical yield given moles (or mass + molar mass) of two reactants and their stoichiometric coefficients.

### Reactant A

Mass of Reactant A (g)

Molar Mass of Reactant A (g/mol)

Stoichiometric Coefficient of A

### Reactant B

Mass of Reactant B (g)

Molar Mass of Reactant B (g/mol)

Stoichiometric Coefficient of B

### Product

Molar Mass of Product (g/mol)

Stoichiometric Coefficient of Product

Calculate

function limCalc() { const resultDiv = document.getElementById("lim-result");

const massA = parseFloat(document.getElementById("lim-massA").value); const mmA = parseFloat(document.getElementById("lim-mmA").value); const coeffA = parseFloat(document.getElementById("lim-coeffA").value);

const massB = parseFloat(document.getElementById("lim-massB").value); const mmB = parseFloat(document.getElementById("lim-mmB").value); const coeffB = parseFloat(document.getElementById("lim-coeffB").value);

const mmP = parseFloat(document.getElementById("lim-mmP").value); const coeffP = parseFloat(document.getElementById("lim-coeffP").value);

// --- Validation --- if (isNaN(massA) || massA Enter a valid mass for Reactant A (≥ 0)."; return; } if (isNaN(mmA) || mmA Enter a valid molar mass for Reactant A (> 0)."; return; } if (isNaN(coeffA)|| coeffA Enter a valid stoichiometric coefficient for A (> 0)."; return; }

if (isNaN(massB) || massB Enter a valid mass for Reactant B (≥ 0)."; return; } if (isNaN(mmB) || mmB Enter a valid molar mass for Reactant B (> 0)."; return; } if (isNaN(coeffB)|| coeffB Enter a valid stoichiometric coefficient for B (> 0)."; return; }

if (isNaN(mmP) || mmP Enter a valid molar mass for the Product (> 0)."; return; } if (isNaN(coeffP)|| coeffP Enter a valid stoichiometric coefficient for the Product (> 0)."; return; }

// --- Core Calculations --- // Moles of each reactant const molesA = massA / mmA; // n_A = m_A / M_A const molesB = massB / mmB; // n_B = m_B / M_B

// Mole ratio: how many moles of B are needed per mole of A consumed // From stoichiometry: coeffA mol A reacts with coeffB mol B // Moles of B required to fully consume all of A: const molesB_required = molesA * (coeffB / coeffA); // Moles of A required to fully consume all of B: const molesA_required = molesB * (coeffA / coeffB);

// Limiting reagent is the one that runs out first // Compare available ratio: molesA/coeffA vs molesB/coeffB // The smaller ratio identifies the limiting reagent const ratioA = molesA / coeffA; const ratioB = molesB / coeffB;

let limitingReagent, excessReagent; let molesLimiting, molesExcessAvailable, molesExcessRequired, molesExcessRemaining; let massExcessRemaining;

if (ratioA

Parameter Value

Moles of Reactant A ${molesA.toFixed(5)} mol Moles of Reactant B ${molesB.toFixed(5)} mol Limiting Reagent Reactant ${limitingReagent} Excess Reagent Reactant ${excessReagent} Moles of Excess Reagent Available ${molesExcessAvailable.toFixed(5)} mol Moles of Excess Reagent Required ${molesExcessRequired.toFixed(5)} mol Moles of Excess Reagent Remaining ${molesExcessRemaining.toFixed(5)} mol Mass of Excess Reagent Remaining ${massExcessRemaining.toFixed(4)} g Percent Excess ${percentExcess.toFixed(2)} % Moles of Product (Theoretical Yield) ${molesProduct.toFixed(5)} mol Mass of Product (Theoretical Yield) ${massProduct.toFixed(4)} g `; }

#### Formulas Used

Moles from mass: n = m / M (mol = g ÷ g·mol⁻¹)

Identifying the limiting reagent: Compare the mole-to-coefficient ratios for each reactant: ratioA = nA / a | ratioB = nB / b The reactant with the smaller ratio is the limiting reagent.

Moles of excess reagent required: nB,required = nA × (b / a) (and vice-versa)

Moles of excess reagent remaining: nexcess,remaining = nexcess,available − nexcess,required

Percent excess: % excess = [(navailable − nrequired) / nrequired] × 100

Theoretical yield (moles of product): nP = (nlimiting / coefflimiting) × coeffP

Theoretical yield (mass of product): mP = nP × MP

where: a, b = stoichiometric coefficients of A and B; coeffP = stoichiometric coefficient of product; M = molar mass.

#### Assumptions & References

The reaction goes to completion (100 % conversion of the limiting reagent).
Only two reactants and one product are considered; extend the ratio method for more complex reactions.
Method follows standard general-chemistry stoichiometry: Zumdahl & Zumdahl, Chemistry, 10th ed., Cengage, 2018, Ch. 9.
Molar masses can be obtained from the IUPAC periodic table: iupac.org.

Limiting Reagent Calculator

Limiting Reagent Calculator

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