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The limiting reagent (or limiting reactant or limiting agent) in a chemical reaction is a reactant that is totally consumed when the chemical reaction is completed. [ 1 ] [ 2 ] The amount of product formed is limited by this reagent, since the reaction cannot continue without it.
However, the definitions of the total amount of reactant to form a product per total amount of reactant consumed is used (Definition 2) as well as the total amount of desired product formed per total amount of limiting reactant consumed (Definition 3). This last definition is the same as definition 1 for yield.
The limiting reagent is the reagent that limits the amount of product that can be formed and is completely consumed when the reaction is complete. An excess reactant is a reactant that is left over once the reaction has stopped due to the limiting reactant being exhausted.
Stoichiometric equations are used to determine the limiting reagent or reactant—the reactant that is completely consumed in a reaction. The limiting reagent determines the theoretical yield—the relative quantity of moles of reactants and the product formed in a chemical reaction. Other reactants are said to be present in excess.
Reagents, such as sulfur (pictured), are the starting materials used in chemical reactions.. In chemistry, a reagent (/ r i ˈ eɪ dʒ ən t / ree-AY-jənt) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. [1]
In addition, for a single reaction a conversion may be defined in terms of the limiting reactant, for the simple decomposition that is species ...
r is the stoichiometric ratio of reactants, the excess reactant is conventionally the denominator so that r < 1. If neither monomer is in excess, then r = 1 and the equation reduces to the equimolar case above. The effect of the excess reactant is to reduce the degree of polymerization for a given value of p.
The extent of reaction is a useful quantity in computations with equilibrium reactions. [citation needed] Consider the reaction 2 A ⇌ B + 3 C. where the initial amounts are = , = , = , and the equilibrium amount of A is 0.5 mol. We can calculate the extent of reaction in equilibrium from its definition