Question

Rusting of iron is a chemical change because _________ .

• A. a new substance with new properties is produced.
• B. the chemical composition of reactant is changed.
• C. the change is permanent and cannot be reserved easily.
• D. the change is temporary and can be reserved easily.

Answer 1

Answer: (A), (B), (C)

The correct options are
A a new substance with new properties is produced.
B the chemical composition of reactant is changed.
C the change is permanent and cannot be reserved easily.

Iron reacts with oxygen in presence of water and undergoes a chemical change/reaction to give a new compound.
This is known as hydrated iron oxide; commonly called as rust.
Its chemical formula is ${\text{Fe}}_2{\text{O}}_3.x{\text{H}}_2\text{O}$. The reaction involved is:
$4{\text{Fe(s) + xH}}_2{\text{O(l) + 3O}}_2\left(g\right)\to {\text{2Fe}}_2{\text{O}}_3.{\text{xH}}_2\text{O(s)}$.
This change is permanent and hence, irreversible in nature.