J.R. S. answered 03/21/19
Ph.D. University Professor with 10+ years Tutoring Experience
4Fe + 3O2 ==> 2Fe2O3
19.2 g O2 x 1 mole O2/31.998 g = 0.600 moles O2
Since according to the balanced equation, 4 moles Fe react with 3 moles O2, the moles of Fe that were used would be 0.600 moles O2 x 4 moles Fe/3 moles O2 = 0.800 moles of Fe
To convert this to mass of Fe, we use the atomic mass of Fe which is 55.8 g/mole
Mass of Fe used = 0.800 moles Fe x 55.8 g/mole = 44.6 g of Fe were used
Yes, this would be considered a physical science question, because it involves principles of chemistry, and chemistry is considered a physical science.