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.

book cover

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.

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