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South African Journal of Chemistry

On-line version ISSN 1996-840X
Print version ISSN 0379-4350

S.Afr.j.chem. (Online) vol.62  Durban  2009




An approach to dealing with the difficulties undergraduate chemistry students experience with stoichiometry



Fiona Marais; Sandra Combrinck

Department of Chemistry, Tshwane University of Technology, Private Bag X680, Pretoria 0001, Republic of South Africa




Chemistry for first year students has been identified by Tshwane University of Technology as one of the subjects with a low pass rate. It is apparent that students often memorize formulae and definitions, without understanding the underlying concepts required to work with abstract units of measure. We have found that the majority of students at this university are unable to balance reaction equations satisfactorily. They are also unable to predict the reaction yield, or identify limiting reagents. It is imperative that these and other related problems are overcome before any meaningful change to the high failure rate at first year level will be realized. All conventional forms of lecture presentation failed to make any significant impact on the success rate. Structured worksheets were developed and used, together with tactile models, to address the problems and the initial findings showed a marked improvement. It was discovered that the students' problems originated from their inability to understand the meaning of subscripts and coefficients in chemical equations. The worksheets and the impact they have made on the students' understanding of stoichiometry are shared in this paper.

Key words: Stoichiometry, limiting reagent, worksheets, tactile models



Full text available only in PDF format.



The authors express their thanks and gratitude to the staff of TUT who assisted with the worksheet intervention, Dr Rosalind Gummow (James Cook University, Townsville, Australia) who validated the PWST test, Dr Thapelo Mamiala (University of Stellenbosch) and Dr Marietjie Potgieter (University of Pretoria) for validating the worksheet intervention according to compliance with the programme content, and Dr Marietjie Potgieter for a critical review of this article.



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Received 12 November 2008
Revised 11 February 2009
Accepted 4 March 2009



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