Introductory college chemistry students' understanding of stoichiometry: Connections between conceptual and computational understandings and instruction

Previous research has shown a gap between chemistry students' conceptual and computational understandings of chemistry topics such as gas laws, equilibrium, and reactions. This qualitative study examined the conceptual and computational understandings of stoichiometry of college students enrolled in a large lecture Introductory Chemistry course. Factors that might influence students' understandings were examined to determine their influence.;Possible influential factors examined included students' prior coursework, and their current chemistry instruction. Instruction on stoichiometry was examined through classroom observations, an instructor interview, and review of the course resources. Course exams and out-of-class assignments were also examined for their influence on students.;Student volunteers (n = 6) were interviewed to gauge their understanding of stoichiometry. Students' understanding was assessed through tasks that included a card sort, solving conceptual and computational problems, drawing representations of reactions, and answering questions concerning their philosophy of learning chemistry.;Results indicated that students had an acceptable understanding of the particulate nature of matter but did not apply this knowledge to problem solving. The students were most comfortable solving computational problems where they could apply algorithms learned from their instructor. The students also applied algorithms in answering conceptual problems. There appeared to be a connection between the students' conceptual structures of stoichiometry and their ability to solve computational problems. The lack of conceptual questions in assessment appeared to be a major contributing factor in the students' lack of conceptual understanding because the students discounted the importance of learning aspects of stoichiometry that were not included on exams. Other contributing factors included the computational focus of instruction on limiting reactant problems, textbook presentation, and student exercises.