Undergraduate pre-service chemistry teachers’ conceptions about inorganic qualitative analysis

R Hanson

doi:10.4314/ajesms.v8i1.69109

Abstract

The research was a baseline study to determine the perceptions and alternative concepts that pre-service teachers’ have which hinder them from making correct inferences during practical inorganic chemistry experiments. A two-tier qualitative analysis diagnostic instrument (QADI) was developed and used to diagnose and treat the participants’ alternative concepts in inorganic chemistry qualitative analysis. The diagnostic instrument was administered to 78 pre-service teachers in the University of Education, Winneba, Ghana. The study revealed that students’ inabilities to make correct inferences or write and balance equations for suspected reactions correctly were the main hindrances to successful qualitative analytical activities. They often resorted to guess work. The most prevalent conceptions were their inability to predict and distinguish between chalky and gel precipitates especially when aqueous ammonia and sodium hydroxide were used on test samples. They were also unable to distinguish insoluble salts from true precipitates. A post administration of the QADI after the treatment period showed that the intervention worked positively to increase pre-service teachers’ content knowledge in inorganic chemistry and their understanding of inorganic qualitative analytical work. Keywords: alternative concepts, content knowledge, inorganic chemistry, pre-service teachers, qualitative analysis

Highlights

Qualitative analysis is a branch of chemistry that deals with the identification of elements or grouping of elements present in a sample
Scored items were incidentally correct options. This was an indication of their understanding of at least certain concepts. It was again an index of their understanding of the questions being asked in the qualitative analysis diagnostic instrument (QADI)
Fe2CO3, NaCl, Al, NaCO3, Na2CO3 etc Conclusion The study showed that pre-service teachers did not have adequate understanding of basic qualitative analysis (QA)

Summary

Introduction

Qualitative analysis is a branch of chemistry that deals with the identification of elements or grouping of elements present in a sample. In some cases it is necessary only to verify the presence of certain elements or groups for which specific tests applicable directly to the sample (e.g., flame tests, spot tests) may be available. More often the sample is a complex mixture, and a systematic analysis must be made in order that all the constituents may be identified. The classical procedure for the complete systematic analysis of an inorganic sample consists of several parts. A preliminary dry test may be performed, which may consist of heating the sample to detect the presence of such constituents as carbon (marked by the appearance of smoke or char) or water (marked by the appearance of moisture) or introducing the sanmple into a flame and noting the colour produced. After preliminary tests have been performed, the sample is commonly dissolved in water for later determination of anionic constituents

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Conclusion