How do you find the molar mass of "Fe"_2"O"_3Fe2O3?
1 Answer
Here's how you can do that.
Explanation:
As you know, the molar mass of a compound tells you the mass of exactly one mole of said element. You can calculate the molar mass of a compound by using
- its chemical formula
- the molar masses of its constituent elements
In this case, a formula unit of iron(III) oxide,
- two atoms of iron,
2 xx "Fe"2×Fe - three atoms of oxygen,
3 xx "O"3×O
This means that one mole of iron(III) oxide will contain
- two moles of iron,
2 xx "Fe"2×Fe - three moles of oxygen,
3 xx "O"3×O
Now, the molar masses of iron and of oxygen are listed as
M_("M Fe") = "55.845 g mol"^(-1)MM Fe=55.845 g mol−1
M_("M O") = "15.9994 g mol"^(-1)MM O=15.9994 g mol−1
This tells you that one mole of iron has a mass of
overbrace(2 xx "55.845 g")^(color(blue)("the contribution of 2 moles of Fe")) + overbrace(3 xx "15.9994 g")^(color(purple)("the contribution of 3 moles of O")) = "159.6882 g"
So, if one mole of iron(III) oxide has a mass of
M_("M Fe"_2"O"_3) = color(green)(|bar(ul(color(white)(a/a)color(black)("159.6882 g mol"^(-1))color(white)(a/a)|)))
