Question

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

Answer 1

Rust has a molar mass of 159.7 g/mol

Explanation:

`color(magenta)"We will use the formula below to answer the question:"`

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:

`color(brown) ("111.7 g/mol + 48.00 g/mol = 159.7 g/mol")`