Answer:
0.119 moles
Explanation:
molar mass of Fe = 55.845g
to find moles = mass/ molar mass
so moles of Fe = 20/55.845
= 0.358 moles
for the equation you are given
for every three Fe, it produces 1 Fe3O4 , meaning the ratio is 3:1
if you have 0.358 moles of Fe, that means the number of moles of Fe3O4 will equal to one third of that,
thus
moles of Fe3O4 = 1/3 x 0.358 = 0.119
