Queendom Tools

Theoretical Yield & Limiting Reagent Calculator

This tool identifies the limiting reagent and theoretical yield from reactant masses and balanced coefficients, crucial for chemistry students needing to predict product amounts from their pre-lab measurements.

Reactants

Product

How to Use This Limiting Reagent Calculator

  1. Type the coefficients from your balanced equation into each reactant row.
  2. Enter the mass you actually weighed out and the compound's molar mass in g/mol.
  3. Fill in the product's coefficient and molar mass — the tool never guesses a product molar mass.
  4. Press Calculate.
  5. Read the limiting reagent badge, the theoretical yield, and the moles/grams of each reagent left over.

FAQ

Q: How do I find the limiting reagent?

A: Convert each reactant's mass to moles (mass ÷ molar mass), then divide by its balanced coefficient — the smallest moles÷coefficient ratio is limiting; in 2H₂ + O₂ → 2H₂O, 2 mol H₂ ÷ 2 = 1 versus 1 mol O₂ ÷ 1 = 1.

Q: Why isn't the limiting reagent just the reactant with the smallest mass?

A: Because molar mass and coefficients both scale the comparison: 4 g of H₂ is 1.98 mol (MM 2.016) but 4 g of O₂ is only 0.125 mol (MM 32.00), so oxygen runs out first despite identical masses.

Q: What is theoretical yield and how is it calculated?

A: Theoretical yield (g) = (moles_lim ÷ coefficient_lim) × coefficient_product × molar mass_product; it assumes 100% conversion, so percent yield = actual ÷ theoretical × 100.

Q: How do I turn the theoretical yield into a solution concentration?

A: Divide the product moles by the solution volume in litres (M = mol/L) — the Molarity and Molality Solution Concentration calculator takes those moles through dilution and molality conversions for you.