Effect of a Perturbation on the Chemical Equilibrium: Comparison with Le Châtelier's Principle

Torres, Emilio Martínez

doi:10.1021/ed084p516

Cited by 13 publications

(6 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A major issue in the study of chemical equilibrium is the use of Le Chatelier's Principle (LCP) and its application in textbooks (Canagaratna, 2003). Often expressed as "If a chemical system is subjected to a perturbation, the equilibrium will be shifted such as to partially undo this perturbation" (Torres, 2007;p. 516), this principle, because of its ambiguity, often leads to erroneous predictions.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Investigating High School Students’ Understanding of Chemical Equilibrium Concepts

Karpudewan¹,

Treagust²,

Mocerino³

et al. 2016

INT J ENV SCI ED

View full text Add to dashboard Cite

This study investigated the year 12 students' (N = 56) understanding of chemical equilibrium concepts after instruction using two conceptual tests, the Chemical Equilibrium Conceptual Test 1(CECT-1) consisting of nine two-tier multiple-choice items and the Chemical Equilibrium Conceptual Test 2(CECT-2) consisting of four structured questions. Both these tests were administered before and after the intervention. Students' responses to the items in both the instruments indicated limited understanding of the various concepts related to chemical equilibrium. Less than 50% of the students provided correct responses to four of the nine items in the CECT-1. The total scores in the CECT-1 ranged from 0 to 8 with a mean score of 4.14 (out of a maximum of 9). In the CECT-2 the total scores ranged from 7 to 17 with a mean score of 11.0 out of a maximum score of 22. Almost half the number of students (44.6%) scored less than 50% of the total marks in the CECT-2; only 0% to 42.9% of students scored the maximum possible marks for each of the four items while achievement in all four items of the CECT-2 was below 50%. The findings will be valuable and assist teachers in planning their instruction on chemical equilibrium by taking into consideration students' preconceptions about the topic.

show abstract

Section: Theoretical Backgroundmentioning

confidence: 99%

Investigating High School Students’ Understanding of Chemical Equilibrium Concepts

Karpudewan¹,

Treagust²,

Mocerino³

et al. 2016

INT J ENV SCI ED

View full text Add to dashboard Cite

show abstract

“…

…”

mentioning

confidence: 99%

The Adverse Effects of Le Châtelier's Principle on Teacher Understanding of Chemical Equilibrium

Cheung

2009

J. Chem. Educ.

View full text Add to dashboard Cite

Chemistry education researchers have noted the inadequacy of Le Châtelier's principle (LCP) for decades (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). They have shown how apparently reasonable applications of LCP can result in incorrect predictions about the effects of changes in concentration, volume, pressure, or temperature on chemical systems at equilibrium. Because LCP has no value for chemistry teachers and students other than historical interest, some researchers (13-19) have criticized the over-emphasis of LCP in the school chemistry curriculum. They have recommended the use of the equilibrium law, reaction quotient, and van't Hoff equation to predict the direction in which a chemical equilibrium system will shift when it is disturbed. Yet little progress has been made to delete LCP from the school chemistry curriculum. Textbooks of high school chemistry or college chemistry published in many countries such as the United States, the United Kingdom, Australia, Canada, and China still rely on LCP as the major predictive tool. Le Châtelier himself described three different statements of LCP (18). Petrucci, Harwood, and Herring (20) emphasized that it is hard to state LCP unambiguously, but they believed that the essential meaning of LCP is as follows: When an equilibrium system is subjected to a change in temperature, pressure, or concentration of a reacting species, the system responds by attaining a new equilibrium that partially offsets the impact of change (20, p 641; emphasis in original).

show abstract

“…Examples are Berger & Mellon (1996), Grant (1984), Last & Slade (1997), and Russell (1988). However, the limitations of LCP are well documented in the literature (Allsop & George, 1984;Bridgart & Kemp, 1985;Canagaratna, 2003;Cheung, 2004;De Heer, 1957, 1958Ehrenfest, 1911;Epstein, 1937;Gold & Gold, 1984Katz, 1961;Lacy, 2005;Levine, 2002;Posthumus, 1933;Quílez, 2004;Raveau, 1909;Sandler, 1999;Solaz & Quílez, 2001;Torres, 2007;Uline & Corti, 2006;Wright, 1969). Any attempt to teach LCP in high school is, in our opinion, a waste of time.…”

Section: Discussionmentioning

confidence: 99%

“…LCP fails to predict such an equilibrium shift. Actually, chemistry education researchers and chemists have known of the scientific inadequacies of LCP for about 100 years (Allsop & George, 1984;Bridgart & Kemp, 1985;Canagaratna, 2003;De Heer, 1957, 1958Ehrenfest, 1911;Epstein, 1937;Gold & Gold, 1984Katz, 1961;Lacy, 2005;Levine, 2002;Posthumus, 1933;Quílez, 2004;Raveau, 1909;Sandler, 1999;Solaz & Quílez, 2001;Torres, 2007;Uline & Corti, 2006;Wright, 1969). They have shown how apparently reasonable applications of LCP can lead to incorrect predictions about the effects of changes in concentration, volume, pressure, or temperature on chemical systems at equilibrium.…”

Section: Introductionmentioning

confidence: 99%

Teachers’ Misconceptions About the Effects of Addition of More Reactants or Products on Chemical Equilibrium

Cheung

Yang

2009

Int J of Sci and Math Educ

View full text Add to dashboard Cite

The importance of research on misconceptions about chemical equilibrium is well recognized by educators, but in the past, researchers' interest has centered on student misconceptions and has neglected teacher misconceptions. Focusing on the effects of adding more reactants or products on chemical equilibrium, this article discusses the various misconceptions held by high school teachers. A misconception test was administered to two samples of chemistry teachers in Nanjing, China. Of the 109 teachers who participated in the test, only one understood that adding more CS 2 gas to the equilibrium system CS 2 (g) + 4H 2 (g) ⇌ CH 4 (g) + 2H 2 S(g) at constant pressure and temperature can shift the equilibrium to the reactant or product side, depending upon the amount of CS 2 in the initial equilibrium system. Most of the teachers relied on Le Châtelier's principle and thus made erroneous predictions. The misconception test also revealed that those teachers who managed to compute equilibrium constants had a limited conceptual understanding of chemical equilibrium. Implications of these findings for teacher education and chemistry curriculum development are discussed.

show abstract

Effect of a Perturbation on the Chemical Equilibrium: Comparison with Le Châtelier's Principle

Cited by 13 publications

References 17 publications

Investigating High School Students’ Understanding of Chemical Equilibrium Concepts

Investigating High School Students’ Understanding of Chemical Equilibrium Concepts

The Adverse Effects of Le Châtelier's Principle on Teacher Understanding of Chemical Equilibrium

Teachers’ Misconceptions About the Effects of Addition of More Reactants or Products on Chemical Equilibrium

Contact Info

Product

Resources

About