We are at last ready to use balanced equations in a practical way to answer some questions about amounts of substances that must be mixed to obtain a given amount of desired product. It is important to state here that the calculations we will be able to do when we are finished here always present the theoretical maximum amounts that must be used or can be obtained.

The reason for this disclaimer is tied up with one of the four questions which this course seeks to address, namely: If a chemical reaction occurs, when does it stop? Since not all chemical reactions can be counted upon to "go to completion", we must recognize that when we make predictions.

The quantitative study of chemical reactions is known as stoichiometry . The calculations in stoichiometry are based upon 2 ideas.