Stoichiometric Factors I

	Stoichiometry Module: General Stoichiometry

Table of Contents

General Stoichiometry

Limiting Reactants

Chemical Analysis

Stoichiometric Factors

In the previous section, it was relatively easy to predict that 14 moles of water would be produced if seven moles of methane were burned:

1 mole		2 moles
7 moles		14 moles

A stoichiometric factor gives a mathematical approach to looking at these types of problems. While the above example was relatively simple to do in your head, it could have been written out mathematically:

Move mouse over terms in equation.

The stoichiometric factor will always have the same form, with the unknown material (and its stoichiometric coefficient (X) from the balanced chemical equation) in the numerator and the known material (and its stoichiometric coefficient (Y) from the balanced chemical equation) in the denominator.

Move mouse over terms in equation.

What are known and unknown materials?

If you wanted to know how much oxygen was needed to burn 12 moles of methane, what stoichiometric factor would you use? (Clicking on check will show chemical equation)

Good! The complete calculation would look like:

It is often useful to map out a stoichiometry problem. The map for this problem would look like:

This map tells us that there is one step to this problem: calculating how many moles of oxygen will react with the given moles of methane. It also tells us that this step can be made by using the stoichiometric ratio (or mole factor).

Remember that the stoichiometric factor will always take on the form:

In this case, our known material is methane (since we know we have 12 moles of it) and our unknown material is oxygen (since we want to calculate how much the methane will produce).