A Conceptual Approach to Limiting-Reagent Problems

Abstract

A solid foundation of chemistry principles is only gained through a true comprehension of the material as opposed to pure memorization. One of the most fundamental concepts in chemistry is that of determining the amount of product formed in a chemical reaction when one of the reactants is limiting. To increase students' comprehension of this important concept, a conceptual approach is presented that is tangible for limiting-reagent problems on the molecular level and extends directly to typical examples that would be encountered in a classroom or laboratory setting. To accommodate visual learners, a graphical methodology is incorporated that determines the limiting reagent as the reactant that is exhausted first while simultaneously finding the amounts of the excess reagents and products.

A Hands-On Activity Incorporating the Threefold Representation on Limiting Reactant

“…This activity aims to overcome two common difficulties that students have (1) not being able to establish connections between the submicroscopic representation of a chemical reaction and the macroscopic observations , and (2) identifying the reactant in the smallest amount of matter as the limiting reactant. , To address these difficulties, students explored the reaction of CuSO 4 with NaOH at the macroscopic, submicroscopic, and symbolic levels of representation.…”

“…The limiting reactant “is the reactant that is exhausted first” during a chemical reaction. This happens because chemicals react according to fixed mole ratios; in other words, they react stoichiometrically .…”

“…The analogy was followed by a chemistry example involving mole quantities and, finally, presenting a situation starting with the mass of the reactants in grams. In another work, Sostarecz and Sostarecz introduced a conceptual approach that incorporates a visual representation through the use of graphs to determine the limiting reactant in a reaction. In a different investigation, Nakhleh and Postek used the concept of limiting reactant to study the impact that the use of multiple representations had on students’ learning.…”

Using Audience Response Systems during Interactive Lectures To Promote Active Learning and Conceptual Understanding of Stoichiometry

“…These systems consist of software, an immediate response card, and a receiving antenna, − and can be used to develop interactive lessons. Although a number of articles have reported the use of personal response systems, and numerous studies can be found about teaching stoichiometry, − this article presents a method involving both subjects that provides information about the impact of cooperative social interactions on learning stoichiometry.…”

Reaction Extrema: Extent of Reaction in General Chemistry

“…Many articles in this Journal have addressed the concept of extent of reaction. − Dumon et al, Peckham, and Croce formulated equations for reactions that go from zero to the maximum extent of reaction. Other authors, for example, Treptow, used a definition such that the reaction extent ranges from “zero” at the beginning of the reaction to “one” at the end.…”