Limiting Reagent
Updated 2026-08-02
INTRODUCTION
English translation pending.
CORE DEFINITION
A basic concept in stoichiometry. In a chemical reaction, the reactant that is exhausted first limits how much product can form, regardless of how much of the other reactants is present. Amounts must be compared in moles against the balanced equation rather than by mass, since the stoichiometric ratio determines which reactant is in shortest supply relative to what the reaction consumes. Excess reactants remain unreacted.
SCAFFOLDING EFFECT
Reduce cognitive load
- Find the constraint: identify which input runs out first rather than which one you have least of by volume - Compare in matching units: convert all inputs into the unit the process actually consumes before comparing - Recheck as you scale: the binding constraint shifts as inputs change, so re-identify it regularly
Anchor fast decisions
A reaction consumes reactants in a fixed ratio, so the one whose available amount falls shortest relative to that ratio stops the process when it is exhausted. Nothing downstream can compensate, because the other inputs cannot substitute for it. Output is therefore capped by the scarcest input measured in the units the process consumes, not by the largest absolute quantity.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Limiting_reagentverified
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