Answer:
Given the reaction:
Fe+H
2
O→Fe
3
O
4
+H
2
If the number of electrons lost or gained during the changes is x. Then, the value of x is 8.
The balanced chemical equation is as follows:
3Fe+4H
2
O→Fe
3
O
4
+4H
2
The oxidation number of hydrogen changes from +1 (in water) to 0 (in hydrogen molecule).
Thus, net change in the oxidation number of hydrogen per atom is 1.
There are 8 H atoms.
Hence, the total change in the oxidation number of 8 hydrogen atoms is 8.
Hence, 8 electrons are involved in the redox reaction.
Hence, x=8.