Which equation represents a reaction that provides the heat of formation of Fe3O4? (Just write A,B, C, D, or E on the answer sheet)
a) 3 Fe(s) + 4 O(g) ---> Fe3O4 (s) b) 6 Fe(g) + 2 O2(g) ---> 2 Fe3O4 (s)
c) 3 FeO(s) + H2O(g) ---> Fe3O4 (s) + H2(g) d) 3 Fe(s) + 2 O2(g) ---> Fe3O4 (s)
e) Fe(s) + 2/3 O2(g) --> 1/3 Fe3O4 (s)