3
$\begingroup$

I am doing a problem that has its answers stated separately for a) and b). One says that $X$ is a limiting reagent and one says $Y$ is a limiting reactant.

My question is, is there a difference between "limiting reagent" and "limiting reactant"? If so, how does these nomenclatures differ, and for what reason does it differ.

Improve this question
$\endgroup$
1
  • $\begingroup$ In that particular use there is no difference. You might look at the definition in the Wikipedia. $\endgroup$
    – Buck Thorn ♦
    Commented Aug 2 at 9:46

2 Answers 2

Reset to default
5
$\begingroup$

"Reagent" refers to any substance involved in a chemical reaction. This can include catalysts, solvents, emulsifiers, or reactants. Essentially, "reagent" is a broader term used for any substance in a chemical reaction.

However, "reactant" only refers to substances that actively take part in a chemical reaction and are converted into products. If a substance is present in a chemical reaction but is not converted into a product, it is not a reactant; instead, it is called a reagent.

If a reagent is consumed in a chemical reaction, it does not necessarily mean it is a reactant. For example, if a reaction occurs in a solvent and some of the solvent evaporates, this does not mean that the solvent is a reactant. For a substance to be considered a reactant, it must be converted into a product.

Therefore, you should look at the balanced chemical equation for the reaction. The substances on the left side of the equation are called reactants, and those on the right side are called products.

Improve this answer
$\endgroup$
1
  • $\begingroup$ I prefer the definition provided by the Wikipedia, in particular it argues that if something is consumed in a reaction it is by definition a reactant, and that solvent, if inert, is neither reactant nor reagent. Otherwise the terms reactant and reagent are mostly interchangeable, although there might be a subtle difference in use. $\endgroup$
    – Buck Thorn ♦
    Commented Aug 2 at 9:44
4
$\begingroup$

The difference is more linguistic, based on the point of view.

For

$$\ce{A + B -> C + D}$$

B may be consider a reactant, but for

$$\ce{A ->[+B][-D]C}$$

B may be considered as a reagent, "making C from A".

Additionally, a reagent may not be a single substance, but a mixture dissolved in a solvent, often used for qualitative analysis, or preparing samples for further analysis. Typical are the Fehling or Benedict reagents to detect reducing sugars.

The adjective "limiting" means for both that the reaction extent is determined by the content of the respective limiting reactant/reagent that is spent sooner, because the other reactant is in excess.

If there is the reactant $\ce{A}$ reacting with the reagent $\ce{B}$ in the molar ratio 1:1, then

  • if A:B ratio is 1:2 then $\ce{A}$ is the limiting reactant.
  • if A:B ratio is 2:1 then $\ce{B}$ is the limiting reagent.
Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.