Lowell High School Chemistry Stoichiometry Online Tutorial — scroll down for sample problem

 What is Stoichiometry? 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 usually determines how much of a substance is expected to react or be produced in a chemical reaction. It is a very mathematical part of chemistry, so get your calculator ready!   Jeremias Benjamin Richter (1762-1807) was the first to describe the law of definite proportions, or stoichiometry. (He also came up with the concept of titrations.) In 1792, he wrote: "Die stšchyometrie (Stšchyometria) ist die Wissenschaft die quantitativen oder MassenverhŠltnisse zu messen, in welchen die chymischen Elemente gegen einander stehen." (German translated into English: Stoichiometry is the science of measuring the quantitative proportions or mass ratios in which chemical elements stand to one another.) Key Terms stoichiometry: mathematical process used to calculate how much you expect to produce from a chemical reaction molar mass: used in stoichiometry to convert from grams to moles and vice versa; units are g/mol limiting reagent: the reactant that limits the amount of products made — based on the moles and the mole ratio of the reactants theoretical yield: calculated amount from stoichiometry you expect to get from the reaction actual yield: real amount from you got from the reaction after carried out by experiment percent yield: how close your actual yield is to what you expected to get