*Saša Aleksij Glažar, Iztok Devetak*
*University of Ljubljana, Faculty of Education, Kardeljeva pl. 16,
1000 Ljubljana*

ABSTRACT

The purpose of this investigation was to evaluate the success and to determine the difficulties faced by Slovene secondary school students (age 19) in solving stoichiometry problems. The data were collected at the Matura exam over a five-year period (1995–1999). A general model for stoichiometry problem-solving was formed. On average, 46 % of students correctly solved the task, while almost 4 % of students did not even attempt to solve it. The most common mistakes in solving stoichiometry problems were in using symbolic chemical language and in calculating the amount ratio. Guidelines for teachers are given on how to improve students´ chemical problem-solving strategies, in order to diminish the range of such mistakes in solving stoichiometry problems.