# How many moles of iron oxide are present in a mass of 16*kg?

Well the molar mass of ferric oxide, $F {e}_{2} {O}_{3}$, is $159.69 \cdot g \cdot m o {l}^{-} 1$....
But iron has a particularly rich oxidation chemistry. We don't know whether all the $16 \cdot k g$ mass was ferric oxide, or ferrous oxide, or $F {e}_{3} {O}_{4}$ or hydrous iron oxides.....Clearly you can work out the molar quantity if all the rust is present as $F {e}_{2} {O}_{3}$....
"Moles of ferric oxide"=(16xx10^3*g)/(159.69*g*mol^-1)=??mol.