Question

write the balanced reaction: iron reacts with steam to form iron oxide and hydrogen

Answer 1

First of all, the basic equation will be:

Fe + H₂O → Fe₂O₃ + H₂

The balanced equation will be:

2 Fe(s) + 3 H₂O(g) → Fe₂O₃(s) + 3 H₂(g)

Answer 2

$\bold{3 \mathrm{Fe}(\mathrm{s})+4 \mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \rightarrow \mathrm{Fe}_{3} \mathrm{O}_{4}(\mathrm{s})+4 \mathrm{H}_{2}(\mathrm{g})}$

When ‘iron’ reacts with steam it forms “iron (II, III) oxide” and also released “hydrogen gas”.  

Here “iron (II, III) oxide” can be formulated as $\mathrm{Fe}_{3} \mathrm{O}_{4}$ therefore the reaction must be:

$\bold{\mathrm{Fe}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \rightarrow \mathrm{Fe}_{3} \mathrm{O}_{4}(\mathrm{s})+\mathrm{H}_{2}(\mathrm{g})}$

Now to balance this reaction we need to add coefficient with each one of the reactant and product to make sure that the ‘number of atoms’ will be same at both sides.  

Hence the balance chemical equation will be:

$\bold{3 \mathrm{Fe}(\mathrm{s})+4 \mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \rightarrow \mathrm{Fe}_{3} \mathrm{O} 4(\mathrm{s})+4 \mathrm{H}_{2}(\mathrm{g})}$