Question

How many moles are in 62 grams of iron (III) oxide, Fe2O3?

Answer 1

The formula that relates number of moles, n, and mass, m, is:

`M=(m)/(n)`

Where M is the molecular weight of the compound we are working with.

In this case, we have Fe₂O₃, and we can calculate its molecular weight using the atomic weghts of Fe (iron) and O (oxygen):

`\begin{gathered} M_(Fe_2O_3)=2\cdot M_(Fe)+3\cdot M_O \\ M_(Fe_2O_3)=2\cdot55.845g/mol+3\cdot15.9994g/mol \\ M_(Fe_2O_3)=(111.69+47.9982)g/mol \\ M_(Fe_2O_3)=159.6882g/mol \end{gathered}`

Now, solving the equiation for n and substituting the molecular weight and the given mass, we have:

`n=(m)/(M)=(62g)/(159.6882g/mol)=0.38825\ldots mol\approx0.38mol`

Thus, 62 grams of iron (III) oxide is approximately 0.38 moles.