What weight of iron metal will be required to produce 20.8g of iron(III)oxide in the reaction with pure oxygen

Answer 1

This is a very simple problem: you can just use the ratio of the weight of the iron vs iron III oxide to get the answer:

20.8g x (2 x 55.85)/[2 x 55.85 + (3 x 16.00)] = 14.5g