This reaction can be written in the form of a word equation as:
`"Iron"+"Steam"to "Iron"(II,III)"oxide"+"Hydrogen"`
Now, Symbol of iron is `Fe`
`"Formula of steam is" H_(2)O" "("It is the same as water")`
`"Formula or iron (II,III) oxide is" Fe_(3)O_(4)" "(Given)`
And, Formula of hydrogen is `H_(2)`
By writing the symbols and formulae of all the substances in the above word equation, we get the following skeletal chemical equation:
`" "Fe+H_(2)OtoFe_(3)O_(4)+H_(2)`
Here Fe and `H_(2)O` are reactants whereas `Fe_(3)O_(4)and H_(2)` are the products. Let us count the number of atoms of various types in the reactants and products :
`{:(,"In reactants","In products"),("No . of Fe atoms:",1,3),("No . of H atoms:",2,2),("No . of O atoms:",1,4):}`
We can see that the number of iron atoms on the left side of the equation is only 1 but there are 3 iron atoms on the right side. Now, to have 3 iron atoms on the left side, we multiply Fe by 3 and write it as 3Fe. Thus,
`" "3Fe+H_(2)Oto Fe_(3)O_(4)+H_(2)`
Let count the number of various types of atoms on both the sides again :
`{:(,"In reactants","In products"),("No . of Fe atoms:",3,3),("No . of H atoms:",2,2),("No . of O atoms:",1,4):}`
Now the number of iron atoms is equal on both side (3 each) and the number of hydrogen atoms also equal (2 each). But the number of oxygen atoms is not equal. There is only 1 oxygen atom on the left side but 4 oxygen atoms on the right side. So, to have 4 oxygen atoms on the left side, we multiply `H_(2)O` by 4 and write it as `4H_(2).` This will give us :
`" "3Fe + 4H_(2)Oto Fe_(3)O_(4)+H_(2)`
Let us count the number of various atoms on the two sides once again:
`{:(,"In reactants","In products"),("No . of Fe atoms:",3,3),("No . of H atoms:",8,2),("No . of O atoms:",1,4):}`
The number of hydrogen atoms now becomes unequal. There are 8 hydrogen atoms on the left side but only 2 hydrogen atoms on the right side. Now, to gel 8 hydrogen atoms on the right side, we multiply `H_(2)` by 4 and write it as `4H_(2).` This given us the following equation :
`" "3Fe+4H_(2)OtoFe_(3)O_(4)+4H_(2)`Let us count the number of various types of atoms on both the sides of this equation:
`{:(,"In reactants","In products"),("No . of Fe atoms:",3,3),("No . of H atoms:",8,8),("No . of O atoms:",4,4):}`
The above chemical equation contains an equal contains an equal number of Fe, H and O atoms in the reactants and Iron (Fe) is a solid, steam `(H_(2)O)` is a gas, iron (II,III) oxide `(Fe_(3)O_(4))` is a solid and hydrogen `(H_(2))` is a gas. So, we can write the above chemical equation with state symbols as follows:
`" "3Fe(s)+ 4H_(2)O(g)to Fe_(3)O_(4)(s)+4H_(2)(g)`
