What is the molar mass of Fe_2O_3 (rust)?

Aug 12, 2016

Rust has a molar mass of 159.7 g/mol

Explanation:

$\textcolor{m a \ge n t a}{\text{We will use the formula below to answer the question:}}$

atomic weight of element $\times$number of atoms given by subscript $=$ molar mass

First, you want to have a periodic table available so you can determine the atomic weight of Fe and O:

• Fe has an atomic weight of 55.85 g/mol
• O has an atomic weight of 16.00 g/mol

From the chemical formula, we have 2 iron atoms. You have to multiply the atomic mass of Fe by 2 to ascertain an atomic weight of 111.7 g/mol

Next, you have 3 oxygen atoms, so you would multiply the atomic mass of O by 3 to obtain an atomic weight of 48.00 g/mol

Now you want to add the mass of each atom together to obtain the molar mass of the entire compound:

$\textcolor{b r o w n}{\text{111.7 g/mol + 48.00 g/mol = 159.7 g/mol}}$