Compute moles, mass and limiting reactant from a balanced chemical equation.
A stoichiometry calculator balances chemical equations and computes the masses, moles, or volumes of reactants and products consumed in a chemical reaction. Stoichiometry is the bookkeeping of chemistry — making sure atoms are conserved and converting between the units chemists use (grams, moles, litres of gas at STP).
The calculator identifies the limiting reagent (the one that runs out first), the theoretical yield (assuming 100% conversion), and percent yield (actual ÷ theoretical × 100) — all the figures you need to plan a synthesis or interpret an experiment.
n = \frac{m}{M} = \frac{V}{22.4} \quad (\text{gas at STP})
Inputs: How much CO₂ is produced when 50 g of CaCO₃ decomposes? CaCO₃ → CaO + CO₂
Split into half-reactions (oxidation and reduction), balance atoms other than O and H, balance O with H₂O, balance H with H⁺ (acid) or OH⁻ (base), balance charge with electrons, then combine the half-reactions so electrons cancel. Practice on a few examples to develop the pattern — once internalised, even complex redox reactions like permanganate titrations balance in a few minutes.
The limiting reagent is the reactant that is consumed first when reactants are not in stoichiometric ratio. Once it is gone, the reaction stops regardless of how much of the other reactants remain. Industrial chemistry deliberately uses excess of cheap reactants so that the expensive one limits the reaction — maximising the use of the costly material.
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