HELPP!! in reaction 3Fe+2O2=Fe3O4 if I add 20g of Fe to my solution how many moles of Fe3O4 will produce???

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