Question

The formation of rust when the Iron is exposed to moist air is called ________.

Answer 1

Corrosion:

• It is the formation of metal oxide when exposed to moist air.
• Corrosion occurs in the presence of moisture. For example, when iron is exposed to moist air, it reacts with oxygen to form rust.
• The reaction proceeds as follows:

The word reaction is: $\mathrm{iron}+\mathrm{water}+\mathrm{oxygen}\to \mathrm{hydrated}\mathrm{iron}\left(\mathrm{III}\right)\mathrm{oxide}$

The balanced chemical reaction is: $$\begin{gathered} 4\mathrm{Fe}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 4\mathrm{Fe}{\left(\mathrm{OH}\right)}_3\left(\mathrm{s}\right) \\ \mathrm{Iron}\mathrm{Oxygen}\mathrm{Moisture}\mathrm{Rust} \end{gathered}$$

• Cathodic protection works to make the corrosion reaction thermodynamically unfavorable
• Corrosion can also occur when metals such as steel are subjected to excessive tension, causing the substance to break.

Hence, the formation of rust when the Iron is exposed to moist air is called corrosion.