12.1. Mole Ratios http://www.ck12.org
MEDIA
Click image to the left for more content.Mole Ratios
Stoichiometry problems can be characterized by two things: (1) the informationgivenin the problem, and (2) the
information that is to be solved for, referred to as theunknown. The given and the unknown may both be reactants,
both be products, or one may be a reactant while the other is a product. The amounts of the substances can be
expressed in moles. However, in a laboratory situation, it is common to determine the amount of a substance by
finding its mass in grams. The amount of a liquid or gaseous substance may also be expressed by its volume. In
this lesson, we will focus on the type of problem where both the given and the unknown quantities are expressed in
moles.
Given substance (mol)→Unknown substance (mol)In the following lesson, “Stoichiometric Calculations,” we will expand our analysis of stoichiometry to include
mass-based and volume-based problems.
Chemical equations express the relative amounts of reactants and products in a reaction. The coefficients of a
balanced equation can represent either the number of molecules or the number of moles of each substance. The
production of ammonia (NH 3 ) from nitrogen and hydrogen gases is an important industrial reaction called the Haber
process (Figure12.1), after German chemist Fritz Haber.
FIGURE 12.1
Nitrogen and hydrogen gases are com-
bined under careful conditions to form
ammonia in a reaction called the Haber
process. Ammonia is a very important in-
dustrial chemical and is produced in very
large quantities, mostly for fertilizers.The balanced equation for the Haber process is: