Question

The number of electrons lost in the following change is-
$Fe + {H_2}O \to F{e_3}{O_4} + {H_2}$
a.2
b.4
c.6
D.8

Answer 1

Hint- Every chemical reaction requiring the transfer of electrons is oxidation. In fact, it requires oxidization of the material that produces electrons. This is normally an oxygen response to a material like carbon. Thus, we will find out the number of electrons lost by examining their oxidation numbers.

Step-By-Step solution:
When we write the balanced chemical reaction of the reaction given in the question, we will get the following reaction-
$3Fe + 4{H_2}O \to F{e_3}{O_4} + 4{H_2}$
From the above reaction it is totally clear that Fe gets converted into $F{e_3}S{O_4}$.
Since there is a loss of electrons, it is clear that oxidation is taking place as in reduction, electrons are gained rather than lost.
When we calculate the oxidation states, we will get the following data-
 Oxidation state of iron in $Fe = 0$
Oxidation state of iron in $F{e_3}S{O_4}$ = $\dfrac{8}{3}$
Now, if we find out the change in oxidation state, we will get-
Change in oxidation state- $\dfrac{8}{3} - 0 = \dfrac{8}{3}$
As we can see from the reaction, Fe is going through oxidation. So-
$ \Rightarrow 3Fe \to F{e_3}{O_4}$
Change of oxidation state of 1 Fe was 8/3
Change of oxidation state of 3 Fe will be-
$ \Rightarrow \dfrac{8}{3} \times 3 = 8$
$ \Rightarrow 3F{e^0} \to F{e_3}{O_4}^{ + \dfrac{8}{3}} + 8{e^ - }$
Thus, the number of electrons lost in the reaction given by the question is 8 electrons.

Hence, option D is the correct option.

Note: Reduction is a chemical reaction that requires electrons being captured from one of the atoms of the two chemicals reactions. The word applies to the product that collects electrons, since its oxidation state is lowered. Oxidation is quite opposite the reduction.