Question

What is the percentage by mass of iron (Fe) in the mineral hematite (`Fe_2O_3`)?

Answer 1

69.9% to three significant figures.

Explanation:

First find the total mass of the compound

`3xx 15.999 = 48` grams for Oxygen

`2 xx 55.8 = 111.6` grams for Iron

adding these gives 159.6 grams per molecules `Fe_2O_3`

Now divide the mass of Iron by the total mass for the compound.

`111.6/159.6 = .6992481` Change this to a percentage by multiplying by 100 and round off to three significant figures gives

69.9 % Iron.