Refresh their stoichiometry

In accordance with the Ontario high school curriculum, students first encounter the topic of stoichiometry in grade 11. In this unit, they are introduced to the mole concept and how it relates to the quantitative aspects of chemical reactions. Students are expected to apply knowledge of chemical equations and the mole theory, along with various mathematical concepts to determine limiting reagents, theoretical yields and experimental yields. For the first time in their lives, we have educators telling grade 11 students that “one plus one does not necessarily make two.”  It is a complex topic, and thus it is unsurprising that many students find it difficult at first.

As the chemistry outreach coordinator and lab instructor at the University of Waterloo, I have the amazing opportunity to interact with hundreds of students at both the high school and university level each term. Accordingly, one of the issues I have repeatedly noticed is that by grade 12, and in their first year of university, a number of students have forgotten many aspects of stoichiometry. I often see students in our laboratory forgetting how to calculate moles of a substrate if the reagent they used is in a liquid state, and many students struggle with chemical reactions that do not exhibit 1:1 stoichiometric relationships.

I believe that students following the Ontario high school curriculum would benefit from re-visiting the concepts of stoichiometry again in grade 12, as it seems that many grade 12 classes do not significantly use this concept in the course. Are you a grade 11 or 12 chemistry teacher?  Do you have thoughts on this topic?