Stoichiometry, Moles, and Molecular Weight
An important manner in which chemists use moles is in stoichiometry. Stoichiometry is the calculation of the quantities and products involved in a chemical reaction.
Consider the Haber process, where atmospheric nitrogen and hydrogen gas are
reacted to form ammonia:
N2(g) + 3H2(g) = 2NH3(g)
In this chemical reaction, the reactants, N2 (nitrogen) and H2
(hydrogen) are both in the gaseous state (hence the "(g)"). The
chemical equation tells you that one molecule of nitrogen reacts with three
molecules of hydrogen to form two molecules of ammonia. It is also true
that one dozen molecules of nitrogen will react with three dozen molecules to
form two dozen molecules of ammonia. Likewise, any multiple involving
these numbers is correct. Chemists usually use moles as their unit of
choice, so it would be correct to say that one mole of N2 reacts with
three moles of H2 to form two moles of NH3.
