How to Calculate Limiting Reagent
What is Limiting Reagent?
The limiting reagent is the reactant that is completely consumed first in a chemical reaction, determining the maximum amount of product that can form. The other reactants are "in excess." Identifying the limiting reagent is essential for calculating theoretical yield.
Step-by-Step Guide
- 1Write and balance the chemical equation
- 2Convert all reactant masses to moles
- 3Divide moles of each reactant by its stoichiometric coefficient
- 4The reactant with the smallest quotient is the limiting reagent
Worked Examples
Input
2H₂ + O₂ → 2H₂O · 4 mol H₂ and 1.5 mol O₂
Result
O₂ is limiting (need 2 mol O₂ for 4 mol H₂)
H₂ ratio: 4/2=2; O₂ ratio: 1.5/1=1.5 → O₂ limits
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