The Meaning of the Word
The word stoichiometry derives from two Greek words: stoicheion (meaning "element") and metron (meaning "measure"). Stoichiometry deals with calculations about the masses (sometimes volumes) of reactants and products involved in a chemical reaction. It is a very mathematical part of chemistry, so be prepared for lots of calculator use.
Jeremias Benjaim Richter (1762-1807) was the first to lay down the principles of stoichiometry. In 1792 he wrote:
"Die stöchyometrie (Stöchyometria) ist die Wissenschaft die quantitativen oder Massenverhältnisse zu messen, in welchen die chymischen Elemente gegen einander stehen."
[Stoichiometry is the science of measuring the quantitative proportions or mass ratios in which chemical elements stand to one another.]
What You Should Expect
The most common stoichiometric problem will present you with a certain amount of a reactant and then ask how much of a product can be formed. Here is a generic chemical equation:
2 A + 2B ---> 3C
Here is a typically-worded problem (often called a "mass-mass" problem):
Given 20.0 grams of A and sufficient B, how many grams of C can be produced?
You will need to use molar ratios, molar masses, balancing and interpreting equations, and conversions between grams and moles. If you struggled with those in class, welcome to the club. Go back and review them if you need to, because if you can't do that stuff, you can't do stoichiometry.
The Steps Involved in Solving Mass-Mass Stoichiometry Problems
The ideas involved will be gone over in detail in other tutorials. The topic usually presented first is the concept of a mole ratio.