Stoichiometry
From the Greek stoikheion "element" and metriฤ"measure."
Here is a good site introducing stoichiometry, with practice problems, from John L. Park's ChemTeam
site.
You might also want to look at the Wikipedia article about stoichiometry here.
Stoichiometry calculations are about calculating the amounts of substances that react and form in a
chemical reaction. For example, based on the balanced chemical equation, we can calculate the
amount of a product substance that will form if we begin with a specific amount of one or more
reactants. Or, you may have a target amount of product to prepare. How much starting compounds
are needed to prepare this amount? These are practical calculations that are done frequently by
chemists.
The Method
For practically all stoichiometry problems, we want to use the. . . .
Fabulous Four Steps
Step 1: Write the balanced chemical equation for the reaction.
Step 2: Calculate the moles of "given" substance. If more than one reactant amount is given,
calculate the moles of each to determine which is the limiting reactant.
Step 3: Calculate the moles of "desired" substance from your answer in Step 2 using the
coefficients from the balanced chemical equation. If more than one reactant was given originally, you
can calculate the moles of product twice, based on the moles of each reactant. The reactant that
gives the smaller moles of product is the limiting reactant. Keep this answer for Step 4.
Step 4: Convert your answer in Step 3 to the units the problem asks for. Usually this is grams,
but it could be volume (for gases or liquid solutions) or concentration (such as molarity, for solutions).
Again in brief:
1. Balanced reaction
2. Moles of "given" substance(s)
3. Moles of "desired" substance such as a product
4. Convert Step 3 answer to the units asked for
