1-It has to be 3 Fe and not Fe3.
2-The oxygens aren't balanced
Balanced equation:
3Fe+4H2O---->Fe3O4+4H2
18)
a. Ra
d. Ag
19)
a. C
b. Br
c. Mg
20)
a. S
b. Br
c. O
Sorry wasn’t sure about some of them in #18
Hope the notes are helpful.
Answer:
Because people on earth may not have the correct technology.
Explanation: