Question

Consider the reaction $Fe + {H_2}O \to F{e_3}{O_4} + {H_2}$
If the number of the electrons lost or gained during the change is $x$ . Then, the value of $x$ is:

Answer 1

In this the first thing important is to write a balanced chemical equation. After that we will have to assign each of the elements their simultaneous oxidation state and at last we can find the difference.

Complete step by step answer: So, the given chemical equation is:
$Fe + {H_2}O \to F{e_3}{O_4} + {H_2}$
And the no. of electrons changed is $x$, then first we have to balance the chemical equation:
$3Fe + 4{H_2}O \to F{e_3}{O_4} + 4{H_2}$
Now the oxidation state of the $H$ is changed from $+ 1$ to $0$ , and the total $H$ atoms are $8$ .
So, the value of the change is $8$ .
We can look at this problem with the different approach by looking at the oxidation state change of $Fe$ from oxidation state of $0$ to $+2$ ,$+3$ and $+3$ that is , it will have two atoms as $Fe^{3+}$ and one of the atom in $Fe^{2+}$ so $3+3+2=8.$
Therefore, $x = 8$ is the answer.

Note:
Most important thing here is to write the balanced chemical equations as it is the initial and generally most careless state. Apart from that it is necessary to find the correct oxidation state on each side of the equation. It is most common mistake of the wrong interconversion of the oxidation states that lead to various wrong answers despite correct execution.