Misconceptions of chemical equilibrium

Those propositions deemed necessary for an understanding of chemical equilibrium and Le Chatelier's Principle were defined by the investigators and validated. Thirty, Year 12 Western Australian chemistry students (17 years of age) who had studied chemical equilibrium were interviewed and students' responses were coded into various categories of misconception that had been identified. The most significant misconceptions revealed by the study were: The rate of the forward reaction increases with time from the mixing of the reactants until equilibrium is established; a simple arithmetic relationship exists between the concentrations of reactants and products at equilibrium; and when a system is at equilibrium and a change is made in the conditions, the rate of the favoured reaction increases but the rate of the other reaction decreases. Students' prior experience of reactions that proceed to completion appears to have influenced their conception of equilibrium reactions; many students failed to discriminate clearly between the characteristics of completion reactions and reversible reactions.