5.2 Stoichiometry

Stoichiometry

Another important aspect of stoichiometry are mole ratios. Under the most elementary form of a chemical equation, the coefficients by the particles represent how many particles of each substance take part in a reaction. However, in stoichiometry, this understanding is translated into that of moles. The coefficients represent how many moles of each substance take part in the reaction relative to one another.

So, in the example of ${2H_2 + O_2 → 2H_2O}$, we can say that for every mole of ${O_2}$ reacted, 2 moles of ${H_2}$ are required and 2 moles of ${H_2O}$ are produced. By the converse, we can also state that for every mole of ${H_2}$ reacted, there is ½ mole of ${O_2}$ required and 1 mole of ${H_2O}$ produced. Remember that a mole is just a quantity the same as a dozen. Although chemical equations and formulas will (almost) always have integer coefficients, moles in stoichiometric calculations do not have to be integers—in fact, they very rarely will be.