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Limiting Reactant Calculator
Enter a complete reaction and the amount of each reactant. The calculator balances the equation, converts the amounts to moles and shows which reactant is exhausted first.
The reactant fields are generated from the left side of the equation.
1 mol N₂ and 2 mol H₂
The balanced equation is N₂ + 3 H₂ → 2 NH₃. One mole of N₂ would need 3 mol of H₂, but only 2 mol are available. H₂ is therefore the limiting reactant. The maximum amount of ammonia is 2 × (2/3) = 1.333 mol NH₃.
Why n/ν identifies the limiting reactant
For each reactant, divide the available amount in moles by its stoichiometric coefficient ν. The smallest value is the maximum reaction extent allowed by that reactant. If two values are equal within rounding, the mixture is stoichiometric rather than having one unique limiting reactant.
Masses are converted to moles using the formula of each reactant. The result is a theoretical maximum; actual experiments can give less product because a reaction may be incomplete or material may be lost.