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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 13 Issue 2 (2008) pp 61-66

Students’ and Teachers’ Inability to Transfer the Molar Concentration Concept to Aqueous Equilibrium Solutions

Juan Quílez

IES Benicalap, Departamento de Física y Química, Nicasio Benlloch, 46015 Valencia, SPAIN, j.quilez@teleline.es
Received June 24, 2006. Accepted May 21, 2007.

Published online: 1 April 2008

Abstract. In this study we report that students as well as teachers inappropriately transfer what they have learned in their study of gaseous equilibrium systems to aqueous equilibrium solutions. Adding water to aqueous equilibria is viewed as: (a) similar to the case involving the addition of solids in heterogeneous equilibria; (b) the addition of one reactant. Those explanations do not consider the increased volume of the solution. Also, the molar concentration concept is not appropriately transferred to the context of aqueous chemical equilibria. Both students and teachers often think that changes in the amount of aqueous equilibrium solutions mean an addition of one of the reactants only. It is concluded that those misconceptions may be derived from the application of simple associative rules that consist of mechanical, algorithmic and limited statements. In addition, a poor representation of the problem, which often reduces the factors to be considered, may be behind the reported misconceptions.

Key Words: In the Classroom; general chemistry; molar concentration; aqueous equilibrium solutions; equilibrium shifts; students’ and teachers’ misconceptions; heuristic rules; equilibrium content knowledge

(*) Corresponding author. (E-mail: j.quilez@teleline.es)

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Issue date: April 1, 2008

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