Question

When steam is passed over red hot iron, the substances formed are:
A.${\text{F}}{{\text{e}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{ + }}{{\text{H}}_{\text{2}}}$
B.${\text{FeO + }}{{\text{H}}_{\text{2}}}$
C.${\text{F}}{{\text{e}}_3}{{\text{O}}_4}{\text{ + }}{{\text{H}}_{\text{2}}}$
D.${\text{F}}{{\text{e}}_3}{{\text{O}}_4}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}$

Answer 1

Hint: Reactants: The compounds which react with each other to form a new compound, are known as reactants.
Products: The compounds which are formed when reactants react with each other, are known as products.

Complete step by step solution:
Generally the compound whose oxidation number increases during the reaction is known as oxidised compound and the compound whose oxidation number decreases during the reaction is known as reduced compound.
Now let us first talk about the oxidations number of elements in the compounds given in the reaction.
Oxidation number of an element: It is defined as the total number of electrons that an atom accepts or loses in order to make a chemical bond which results in the formation of a chemical compound.
Oxidation: The compound which loses the electron during the reaction or the compound whose oxidation number increases during the reaction.
Reduction: The compound which gains the electron during the reaction or the compound whose oxidation number decreases during the reaction.
Now if we write the reaction when steam is passed over red hot iron, the reaction is as:
${\text{3Fe + 4}}{{\text{H}}_{\text{2}}}{\text{O}} \to {\text{F}}{{\text{e}}_{\text{3}}}{{\text{O}}_{\text{4}}}{\text{ + 2}}{{\text{H}}_{\text{2}}}$
Here the products formed are as ferric oxide ${\text{F}}{{\text{e}}_{\text{3}}}{{\text{O}}_{\text{4}}}$ and dihydrogen ${{\text{H}}_{\text{2}}}$.

Here we can say iron is oxidized (because addition of oxygen in iron takes place) and water is reduced (because oxygen is eliminated from water).
So we can define oxidized and reduced compound as:
Oxidized compound: The compound to which oxygen is added during the reaction, is known as oxidized compound.
Reduced compound: The compound from which oxygen is removed during the reaction, is known as reduced compound.

Hence option C is correct.


Note:
Generally the compound which is oxidised in the reaction will act as reducing reagent (which oxidise the other compounds) and the compound which is reduced in the reaction will act as oxidising reagent (which reduce the other compounds) for the reaction.