How do these ion things work?

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

Which statement about hf is true? it is zero for any compound in its standard state. it is positive when the bonds of the product store more energy than those of the reactants. it is negative when a compound forms from elements in their standard states. it is zero for any element that is in the liquid state.

You have a sample of a metal, the sample is exactly 6.02 x 1023atom, if the sample has a mass 55.85 what metal is your sample made of?