Question

iron (III) oxide is formed when iron combines with oxygen in the air, how many grams of Fe2O3 are fomed when 16.7 g of Fe reacts completely with oxygen

Answer 1

4Fe+3O2-->2Fe2O3
number of moles=mass/molecular mass
number of moles of iron=16.7/55.8
ratio of iron to iron oxide is 4:2
so number of moles of iron*2/4=
after you get the number of moles of iron oxide multiply it by its Molecular mass
Molecular Mass of iron oxide :(55.8*2+(16*3)