Question

$Fe_{2} (SO_{4})_{3}$ is empirical formula of a crystalline compound of iron. It is used in water and sewage treatment to aid in the removal of suspended impurities. Calculate the mass percentage of iron, sulphur and oxygen in this compound.

Answer 1

Molecular mass of Fe2(SO4)3= 2X56+3(32+4X16) =400 g/mole 
Mass of oxygen = 3(4X16) = 192 
% of Oxygen = Mass of Oxygen/Molecular mass of Fe2(SO4)3 X 100 
= 192/400 X 100 
= 48% (Answer)

Element  Symbol  Atomic Mass  # of Atoms  Mass Percent
IronFe55.845136.762%
OxygenO15.9994442.129%
SulfurS32.065121.108%

Answer 2

Answer :

mass% of iron =28%

mass% of sulphur =24%

mass % of oxygen =48%