Stoichiometry 2

Concentration

The formula for concentration is $c=\frac{n}{V}$, where $c$ is concentration in $mol{L}^{-1}$, $n$ is number of moles and $V$ is volume.

Limiting reagents

Efficiency

The efficiency of a reaction is determined by the percentage of the reactants which actually react. Take the following example:

$$2{\text{H}}_2^{}+{\text{O}}_2^{}⟶{\text{H}}_2^{}\text{O}$$

Suppose there are $0.3mol$ of $\text{H}$ and only $0.12mol$ of ${\text{H}}_2^{}\text{O}$ is produced.

If the reaction were $100\%$ efficient: $n\left({\text{H}}_2^{}\text{O}\right)=\frac{1}{2}n\left({\text{H}}_2^{}\right)=0.15mol$.

So the efficiency of the reaction can be determined by $\frac{\text{actual number of moles produced}}{\text{expected number of moles produced}}=\frac{0.12}{0.15}=80\%$.

We can also use a given efficiency to calculate the number of moles produced / consumed.

$${\text{H}}_2^{}\text{O}$$