# What is the molar mass of #Fe_2O_3# (rust)?

##### 1 Answer

Aug 12, 2016

#### Answer:

Rust has a molar mass of 159.7 g/mol

#### Explanation:

**atomic weight of element #xx#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: