Question

PLEASE HELP!!
Determine the mass percent of iron in Fe2O3 to four significant figures.

Use the following atomic masses: Fe, 55.85 amu; O, 16.00 amu

Answer 1

All you need to do is divide the mass of iron in Fe2O3 by the total mass of Fe2O3.

You have 2 Fe atoms, so the total mass is 55.85 x 2 = 111.7 amu
The total mass of Fe2O3 is 111.7 + 16 x 3 = 159.7 amu

So, the % mass of iron will be 111.7/159.7 x 100 = 69.94%