Does the Addition of Inert Gases at Constant Volume and Temperature Affect Chemical Equilibrium?

Susana Fonseca
Faculty of Sciences, University of Porto, Portugal
João C. M. Paiva and Jorge Gonçalves
Department of Chemistry, Faculty of Sciences, University of Porto, Portugal;
J. Chem. Educ., 2008, 85 (8), p 1133
DOI: 10.1021/ed085p1133
Publication Date (Web): August 1, 2008

Abstract

In this article we examine three approaches, leading to different conclusions, for answering the question "Does the addition of inert gases at constant volume and temperature modify the state of equilibrium?" In the first approach, the answer is yes as a result of a common students' alternative conception; the second approach, valid only for ideal mixtures of gases, leads to a negative response, and in the third approach the answer is "a little" obtained from a more universal explanation. This last approach, ignored even in advanced chemistry textbooks, is valid for real mixtures of gases and the effects start to become verifiable at moderate pressures. Le Châtelier's principle application to pressure variations is explored in the context of the results from the different approaches.

Keywords (Audience):

First-Year Undergraduate / General

Keywords (Domain):

Physical Chemistry

Keywords (Pedagogy):

Misconceptions / Discrepant Events

Keywords (Subject):

Equilibrium
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History

  • Received: August 03, 2009

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