4.5 Stoichiometry

Stoichiometry

Stoichiometry involves calculations to predict how many products there will be for some given reactants or determining how many reactants are needed to produce a certain amount of products. Stoichiometry takes advantage of molar ratios to convert between products and reactants.

Let’s say you have the reaction:

You are given that you have ${4 \text{ mol } O_2}$ and ${2 \text{ mol } CH_4}$. Since the balanced molecular equation requires ${1 \text{ mol } CH_4}$ and ${2 \text{ mol } O_2}$ to produce the products, ${2 \text{ mol } CH_4 and 4 \text{ mol } O_2}$ will produce ${4 \text{ mol } H_2O}$ and ${2 \text{ mol } CO_2}$.

To convert from moles of ${CH_4}$ to moles of ${H_2O}$, you multiply by the ratio of their coefficients, which is the factor ${\frac{2 \text{ mol } H_2O}{1 \text{ mol } CH_4}}$.

For example: