Limiting Reactant
Definition and meaning of Limiting Reactant in chemistry.
The limiting reactant is the substance in a chemical reaction that is completely consumed first, thereby determining the maximum amount of product that can be formed. Once this reactant is depleted, the reaction abruptly stops, regardless of how much of the other reactants remain.
In more detail
In most practical chemical syntheses, reactants are not mixed in the exact stoichiometric ratios dictated by the balanced equation. One reactant is usually supplied in excess to ensure the complete conversion of the more expensive or crucial reactant. To find the limiting reactant, one must calculate the theoretical yield of a product using the initial amounts of each individual reactant; the one producing the smallest calculated yield is the limiting one. This core concept is essential for accurately calculating theoretical yields and evaluating overall reaction efficiency.
Key facts
| Field | General Chemistry |
|---|---|
| Function | Dictates maximum theoretical yield |
| Related concept | Excess reactant |
If a chemist reacts five moles of hydrogen gas with five moles of oxygen gas to produce water, hydrogen is the limiting reactant because it will run out first according to the reaction stoichiometry.
Frequently asked questions
How do you identify the limiting reactant in a chemistry problem?
Convert the mass of all reactants to moles, divide by their stoichiometric coefficients from the balanced equation, and the smallest value corresponds to the limiting reactant.