Chemistry: Stoichiometry: Fun to Say, Fun to Do!

Stoichiometry: Fun to Say, Fun to Do!

Before I write another paragraph, let's all pronounce the word "stoichiometry" together. Ready, set, "stoy-key-ah-meh-tree." Say it again! Now, say it five times as quickly as you can. I told you it was fun to pronounce!

Molecular Meanings

Stoichiometry is a way of relating the masses or volumes of the reactants and products of a chemical reaction to each other.

Now for the hard question: What does it mean? Stoichiometry is simply a way of relating the masses or volumes of products and reactants in a chemical reaction to each other. Put in a simpler way, it's how we can figure out how much of each ingredient will be needed to make a desired quantity of a final product.

Molecular Meanings

The term excess quantity is common in stoichiometric calculations. This term means that we have a larger than needed amount of the "excess" reactant and a smaller quantity of the other reactant (called the "limiting reactant," but more on that later). As a result, the amount of product that will be formed depends on the other reactant, not the "excess" one.

To illustrate what I mean, let's use another recipe that my wife is fond of (she's not as good a cook as I am, so the recipe is much simpler):

Mrs. Guch's Old-Fashioned Ice Water Recipe

1 glass of water

4 ice cubes

Place ice cubes into water. Makes one glass of ice water.

I told you she wasn't much of a cook. In any case, to prove that you already know stoichiometry, I want you to calculate how many glasses of ice water can be made if I have 5 glasses of water and an excess quantity of ice.

Okay, time's up. If you determined that we could make five glasses of ice water with the specified ingredients, you're already a stoichiometry genius! If you couldn't, then you should go get yourself five glasses of water and a huge sack of ice and perform this experiment to prove to yourself that five glasses is the correct answer.

Excerpted from The Complete Idiot's Guide to Chemistry © 2003 by Ian Guch. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

To order this book direct from the publisher, visit the Penguin USA website or call 1-800-253-6476. You can also purchase this book at and Barnes & Noble.