[eastsherbert8948]

In a reaction represented by:
3Fe + 4H2O --> Fe3O4 + 4H2
How many moles of Fe react if 1kg of H2 is formed?

(I calculated 125 moles of iron react to produce 1 kg of hydrogen gas via 500 divided by 4 (500 being the moles of H2) Thank you

[Hunter2]

No, start with how many mol  is 1 kg H2
Then look  how many moles correspond to the iron.

[Borek]

No, start with how many mol  is 1 kg H2

OP already did that.

[Borek]

(I calculated 125 moles of iron react to produce 1 kg of hydrogen gas via 500 divided by 4 (500 being the moles of H2) Thank you

You started right, but you ignored stoichiometric coefficient for iron.