An oxide of iron contains 70% iron by mass, simplest formula of dioxide is-

A complex of iron contains 45.6% iron by mass. Calculate the number of iron atoms present in 15.0 g of this complex.

Determine the empirical formula of an oxide of iron which has 69.9% iron and 30.1% oxygen by mass. (Atomic mass : Fe = 55.85 amu, O = 16.00 amu).

An oxide of iron is found to contain 69.9% iron and 30.1% dioxygen (O_(2)) by mass. Calculate its empirical formula.