How many moles of Fe2O3 are formed when 55.8 g of Fe reacts completely with oxygen

Using atomic mass of Fe, 55.8g/mol, and mass of 16.7g, we find number of moles in 4Fe.

16.7/55.8 = 0.30moles of 4Fe

Now, we divide this by 2, as we have 2Fe2O3.

0.30/2 = 0.15moles of 2Fe2O3.

We use the molecular mass of 2Fe2O3 (159.6) multiplied by the number of moles (0.15moles), 159.6x0.15 = 23.94g of 2Fe2O3.