For many chemistry students, solving stoichiometry problems is a headache. But it does not have to be that way. In this post, I’m going to show you a simple way to make your stoichiometry story a sunny one.

What we are usually doing with these types of problems is converting some quantity of a substance, usually expressed in grams, to a different unit called a mole. Then we often go from the number of moles of that first substance to the number of moles of another and then, finally, to the amount of that second substance (again, in grams).

I like to think of the process as being like a canyon. You’re starting out in grams land, above one fork of the river, and you have to get down onto the canyon floor and cross not one, but two, mole rivers before you get back up to the other grams land on the other side.

The analogy also works if you start on particle beach (where the atoms and molecules are) or liter overlook. To get to the other particle beach or the other liter overlook, you have got to cross the mole rivers.

So here’s what we do:

The key to successfully reaching the first mole river is to use the right conversion factor.

If you start with grams, you divide the number of grams of the reactant or product (whichever one you are starting with) by the molar mass of the substance. You get that from the Periodic Table of the Elements.

If you start with liters, then you divide the number of liters by 22.4 because, for any gas at standard temperature and pressure (STP), there are 22.4 liters in a mole.

If you start with particles, you divide the number of atoms or molecules with which you are starting by Avogadro’s number.

Okay, so now you are the first fork of the mole river. Now you have to get to the other fork. Here’s where the mole ratio in your balanced chemical equation comes into play. You need to set up a ratio of the moles of a reactant or product (whichever one you are starting with) to the number of moles of the product or reactant (whichever one you are ending up with).

Finally, you go from the moles of that product or reactant or product back to particle beach, liter overlook, or grams land on the other side of the canyon.

To get to particle beach, you multiply the number of moles of reactant or product from the second mole river fork by Avogadro’s number.

To get to liter overlook, you multiply the number of moles of reactant or product that you got to at the second mole river fork by 22.4.

To get to grams land, you multiply the number of moles of reactant or product from the second mole river fork by the molar mass of the compound.

If you follow this path, the story of your canyon crossing will be sweet.