3Fe + 4H2O 1Fe3O4 + 4H2 2.55 x 1025 molecules of H2O will combine with Fe to produce g H2.

124 g of Fe will combine with H2O to produce formula units of Fe3O4.

2.24 moles Fe will fully react with g of H2O.

78.0 g of H2O will react with Fe to produce formula units of Fe3O4.

9.25 x 1023 formula units of Fe will react with H2O to produce moles of H2.