“The task of calcs stoichiometric
Is central to chem’s dialectic.
For reactions, find yield
When this knowledge you wield,
As you monitor products eclectic.”
Another teaching-centered limerick here on Day 4 of this April 2019 project… this one seeks to answer the questions: Why do the concepts of balancing reactions loom so large in so many former chem students’ minds? Why do we spend so much time balancing reactions in the first place? (What are the disciplinary applications of that skill?)
“The task of calcs stoichiometric/
Is central to Chem’s dialectic.”
Once a reaction is balanced, we can do a variety of interesting calculations with it; this is a central theme of introductory chemistry. Learning how to manipulate and use a balanced chemical reaction is the substance of stoichiometry, a word that comes from the Greek for “element” plus “measure.” A balanced reaction gives rise to the proportions of the reactants and products involved.
The 1991 version of Father of the Bride, with Steve Martin’s grocery store tantrum, indirectly provides an introduction to these concepts! In this scene, Martin’s character George has a breakdown when he cannot buy hot dogs and hot dog buns in the same quantities; he dismantles packages of the latter to achieve equivalent amounts of the two.
Here, George’s “balanced reaction” is:
1 Hot Dog + 1 Bun → 1 Hot-Dog-In-Bun.
He erupts when he cannot purchase his “reagents” (ingredients) in the necessary “stoichiometric ratio” (here, one-to-one).
“For reactions, find yield/ When this knowledge you wield/
As you monitor products eclectic.”
One oft-taught application of stoichiometry is predicting the yield of a chemical reaction: how much of a desired product can we obtain, given the starting amounts? (To return to the cinematic scene cited above, since George has eight hot dogs and twelve buns, his maximum “yield” would be eight hot-dogs-in-buns… to his obvious frustration.) If a balanced reaction has multiple reactants and/or products, we can apply stoichiometric principles to any of them.
This opens the door to many valuable calculations: the combination of a balanced reaction and an understanding of the periodic table is a particularly powerful tool to “wield.”
Chemphasis 