Reaction Terminology "In excess"

[VincentLe_3A]

When a problem tells you that a certain molecule reacts with an excess of another molecule, does that mean that the excess of the other molecule is one of the reactants? For example on the last two questions on the Sapling Homework, the problems stated (9)"Caproic Acid is burned in excess oxygen" and (10) "2-butanone was reacted with an excess of propyl magnesiumbromide". I just wanted to clarify the significance of using the term "in/an excess" in chemical reaction problems. Thank you!

[Chem_Mod]

You are correct, the molecule in excess is one of the reactants. In terms of limiting reactants, that means that the other molecule will be the limiting reactant.

[Crystal Yu 1D]

Yes, in this case the problem is simply saying that the Caproic Acid and Oxygen react. Because there is an excess of Oxygen, Oxygen is the excess reactant and Caproic Acid is the limiting reactant. The same thing applies for your other example. 2-Butanone is the limiting reactant. Propyl Magnesiumbromide is the excess reactant.

[Ethan Laureano 3H]

I think the key to these problems would be the words "reacts with" as you won't see reactants reacting with products.

[Crystal Pan 2G]

In excess basically means that there is more than enough of this element to react, and that the other reactant is the limiting reactant.

[Samudrala_Vaishnavi 3A]

If it states "in excess" it refers to the fact that one of the reactants is not the limiting reactant so in excess DOES refer to the reactant. I notice it's common to have a problem analyzing the limiting reactants or anything related to the reactants with combustion reactions.

[Arieanne De Guzman 2J]

Yes they are reactants! When a problem states "burned/reacted with an excess _____", excess means that there is more molecules of that specific reactant in the chemical reaction (some of which will be unused after the reaction has taken place). The other reactant would be the limiting reactant. In the problems you referred to, oxygen would be the reactant in excess while caproic acid would be the limiting reactant and propylmagnesium bromide would be the reactant in excess and 2-butanone would be the limiting reactant.

[IshanModiDis2L]

I believe you have the right idea, "in excess" refers that you have more of that element to react in its lowest form. The molecule in excess is one of the reactants and it means the other reactant/molecule involved is the limiting reactant.

[Nhu Pham-Dis3G]

Yes! In excess just means that once the element with the smallest amount is used up that the element that is in "excess" still is not used up.

[Angelica Soriano 3L]

Yes, when a question refers to something as "in excess" it's a reactant! This means that O2 in this problem isn't completely used up and reacts with caproic acid, which is the limiting reactant.

[Lorraine Jiang 2C]

I believe you are correct if the question says "in excess", then that means the molecule it is referring to is more than proportion than the other reactant molecule (which is the limiting reagent). Hope it helps!

[Chinmayi Mutyala 3H]

Yes! When a reactant is in excess, it means the other reactant is limiting.