First-Year University Chemistry Textbooks’ Misrepresentation of Gibbs Energy

Quílez, Juan

doi:10.1021/ed100477x

Cited by 18 publications

(24 citation statements)

References 40 publications

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“…N is the so-called standard free energy of denaturation, i.e., the rate of change of G with respect to ξ [22,23,24], and RT{(n 0 -ξ) ln[(n 0 -ξ)/n 0 ] + ξ ln(ξ/n 0 )} is the free energy of mixing of the two species. [21] Eq.…”

Section: Discussionmentioning

confidence: 99%

Thermal Denaturation of Proteins and Chemical Equilibrium

Moroni¹,

Gellini²,

Salvi

2015

WJCE

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The thermal denaturation of proteins is considered as a process by means of which chemical equilibrium can be introduced to undergraduate students of Chemistry related curricula. In this approach chemical potential μ, Gibbs energy G, degree of advancement ξ and Le Châtelier principle are integrated with chemical equilibrium. With reference to α-Chymotrypsinogen A as a test case, the process is discussed in terms of a simplified two-state model. The activity is addressed to physical chemistry students in combination with computer-aided work mainly involving storage/manipulation of large data sets and plot preparation.

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Section: Discussionmentioning

confidence: 99%

Thermal Denaturation of Proteins and Chemical Equilibrium

Moroni¹,

Gellini²,

Salvi

2015

WJCE

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“…En la revisión inicial realizada por Quílez (2008) a este respecto, no se encontró ningún trabajo previo que se ocupase de estudiar este problema dentro del contexto español. Sin embargo, en el mismo año de su publicación apareció un nuevo artículo (Centellas, 2008), en el que se analizaba, con ENSEÑANZA DE LAS CIENCIAS, NÚM.…”

Section: Planteamiento Del Problema Y Objetivounclassified

“…En este trabajo solo nos hemos centrado en discutir el segundo de los errores. La expresión correcta es Δ r G º = −RT ln K º (Quílez, 2009;2012). Solo en dos libros de química de nivel preuniversitario (Caamaño et al, 1991;Caamaño et al, 2000) se escribe correctamente esta ecuación.…”

Section: Tratamiento De Las Constantes De Equilibrio En Los Libros Deunclassified

“…Cómo tratan los libros de química el concepto de equilibrio químico se ha analizado, entre otros, por Pedrosa y Dias (2000). La utilización didáctica del principio de Le Chatelier ha sido estudiada por Quílez (1997) y dos trabajos recientes examinan cómo los libros de química general definen y usan los términos asociados a la energía de Gibbs (Quílez, 2009(Quílez, , 2012.…”

Section: Introductionunclassified

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Definición y unidades de las constantes de equilibrio en los libros de texto de Química general preuniversitarios y universitarios

Quílez-Pardo¹,

Quílez-Díaz

2014

ensciencias

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RESUMEN • En este trabajo, una vez definidas las constantes de equilibrio experimentales, K p y K c , así como la constante de equilibrio termodinámica, Kº, se analiza su incorrecto tratamiento por parte de libros de texto de química general. Se expone la forma en que libros de química general de universidad y de bachillerato manejan las unidades de las constantes de equilibrio. Muchos textos no expresan con unidades los valores de K p y K c calculados. Además, en la mayoría de los casos, Kº no se define, y como resultado existe una confusión muy extendida acerca de estos conceptos. Este problema terminológico ocasiona que en muchos libros se confunda K p con Kº. Se propone que la definición correcta de las constantes K p y K c se realice en el nivel preuniversitario, dejando para el primer curso universitario de química general la definición de la constante de equilibrio termodinámica, Kº, así como su relación con K p y K c. PALABRAS CLAVE: Química general; Termodinámica; constantes de equilibrio; análisis de textos. ABSTRACT • In this paper, after presenting the experimental equilibrium constants, K p and K c , and the thermodynamic equilibrium constant, Kº, it is analysed the misrepresentation of them by general chemistry textbooks. We examine the way both first-year university chemistry textbooks and preuniversity chemistry textbooks handle the units of equilibrium constants. Many textbooks do not report the corresponding units in the calculation of K p and K c. Moreover, in most of the cases, Kº is not defined and as a result confusion about these concepts is widespread. This problem in the terminology used by textbooks causes that many of them confuse K p with Kº. It is suggested that preuniversity textbooks should correctly define both K p and K c , leaving the definition of the thermodynamic constant, Kº, as well as its relationship to K p and K c , to first-year university textbooks.

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“…(Note that the familiar claim that the sign of ΔG indicates spontaneity is not quite correct. 1,2 Even so, this claim will be used here to avoid confusion.) When these reactions occur, energy may flow into or out of the system via heat and/or expansion work (i.e., P V work), both of which change the internal energy of the system, U.…”

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confidence: 99%

Enthalpy and the Second Law of Thermodynamics

Keifer

2019

J. Chem. Educ.

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The change in enthalpy of a chemical reaction conducted at constant pressure is equal to the heat of the reaction plus the nonexpansion work of the reaction, ΔH = q P + w additional. After deriving that relationship, most general and physical chemistry textbooks set w additional = 0 to arrive at the claim that ΔH = q P, and nearly all further discussion of enthalpy assumes that ΔH = q P. Setting w additional = 0 is viable for spontaneous reactions, but for nonspontaneous reactions, w additional ≠ 0 as a consequence of the second law of thermodynamics. Therefore, ΔH ≠ q P for nonspontaneous reactions. Moreover, nonexpansion work is important for many interesting and important spontaneous reactions in biology (e.g., muscular movement, nerve signal transmission) and in modern society (e.g., batteries); incorporating w additional into ΔH allows for a more accurate discussion of the energy flow in these reactions. In this paper, I show that ΔH ≠ q P for nonspontaneous reactions, and I discuss how ΔH must be partitioned between q P and w additional for several kinds of reactions according to the second law of thermodynamics. Finally, I suggest how the discussion of enthalpy could be corrected in general and physical chemistry textbooks.

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First-Year University Chemistry Textbooks’ Misrepresentation of Gibbs Energy

Cited by 18 publications

References 40 publications

Thermal Denaturation of Proteins and Chemical Equilibrium

Thermal Denaturation of Proteins and Chemical Equilibrium

Definición y unidades de las constantes de equilibrio en los libros de texto de Química general preuniversitarios y universitarios

Enthalpy and the Second Law of Thermodynamics

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