Teaching Stoichiometry

Many chemistry teachers have strong views on teaching stoichiometry, and I must admit that I'm one of them. I believe a solid emphasis on stoichiometry belongs in all beginning chemistry courses, including non-science major general chemistry. Stoichiometry is not only an important chemistry tool, it's also a major foundation of chemical atomic theory. We cannot see atoms and molecules in the concrete way that we see objects in our daily lives. In this sense, there is an abstract quality to them. Stoichiometry was our first window for looking into this abstract world. It is with stoichiometry that human minds saw atoms and molecules for the first time. And wonder of wonders, we did this using mathematics that most adult humans understand intuitively - simple direct proportion.

This brings me to the subject of pedagogic approaches for teaching stoichiometry. My view here is pretty simple. We make way too much of a big deal out of pedagogic approaches to the mathematics of direct proportion. How about starting with a simple question: If a coin has a mass of 5 grams, what will be the approximate mass of 4 of these coins? For adults who can answer this question, we are ready to move to the essence of the chemistry of stoichiometry.

And that's why I wrote the stoichiometric calculator. Consider what a rare gift we were given back in 1803. Al2(SO4)3 is a self labeling number and Al2/Al2(SO4)3*100 is a self labeled direct proportion chemical calculation as simple as the above coin question. It's the percentage of Al in Al2(SO4)3. The real pedagogy of teaching stoichiometry involves helping students understand that Al2/Al2(SO4)3*100 translates to (Al*2)/(Al*2+(S+O*4)*3)*(100). The pedagogic challenge is chemical not mathematical.