Question

In a 1.143E+2 g sample of iron(III) oxide, how many grams of iron are present? Your answer should have the appropriate number of significant figures (use two decimal places in atomic masses).

Answer 1

Mass of iron(III)oxide, Fe2O3 sample = 1.143*10^2 g

Molar mass of Fe2O3 = 159.69 g/mole

i.e. 1 mole of Fe2O3 weighs 159.69 g

Based on stoichiometry:

1 mole of Fe2O3 has 2 moles of Fe

Atomic mass of Fe = 55.85 g/mole

Therefore we can write:

159.69 g of Fe2O3 is composed of 2*55.85 g of Fe

Thus, amount of Fe present in 1.143*10^2 g sample of Fe2O3 is

= 1.143*10^2 * 2* 55.85/159.69

= 7.995*10^-1 g