Question

What happens when the Iron is kept exposed to a humid atmosphere? Explain the process by writing the chemical equations

Answer 1

• The formation of reddish-brown coating growing on the surface of Iron due to the action of wet air is referred to as rust.
• Rust is a red-brown flaky substance that occurs when an Iron object is exposed to damp air for a long time. This condition is known as rusting.

Chemical reactions:

• Iron is a reducing agent, but Oxygen is an excellent oxidizing agent. When exposed to Oxygen, the Iron atom easily gives away electrons.

$\mathbf{Fe}\mathbf{}\mathbf{\left(}\mathbf{s}\mathbf{\right)}\mathbf{}\mathbf{\to }\mathbf{}{\mathbf{Fe}}^{\mathbf{2}\mathbf{+}\mathbf{}}\mathbf{}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{}\mathbf{+}\mathbf{}\mathbf{2}{\mathbf{e}}^{\mathbf{-}}\mathbf{}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}$

• When water is present; the oxygen atom increases the oxidation state of Iron.

$\mathbf{4}\mathbf{}{\mathbf{Fe}}^{\mathbf{2}\mathbf{+}}\mathbf{}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{}\mathbf{+}\mathbf{}{\mathbf{O}}_{\mathbf{2}\mathbf{}\mathbf{}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}\mathbf{}\mathbf{\to }\mathbf{}\mathbf{4}{\mathbf{Fe}}^{\mathbf{3}\mathbf{+}\mathbf{}}\mathbf{}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{}\mathbf{+}\mathbf{}\mathbf{2}{\mathbf{O}}^{\mathbf{2}\mathbf{-}\mathbf{}}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}$

• Between the Iron cations and the water molecules, the following acid-base reactions occur

${\mathbf{Fe}}^{\mathbf{+}\mathbf{2}\mathbf{}\mathbf{}}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{}\mathbf{+}\mathbf{}\mathbf{2}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}\mathbf{}\mathbf{\left(}\mathbf{l}\mathbf{\right)}\mathbf{}\mathbf{\to }\mathbf{}\mathbf{Fe}{\mathbf{\left(}\mathbf{OH}\mathbf{\right)}}_{\mathbf{2}}\mathbf{}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{}\mathbf{+}\mathbf{}\mathbf{2}{\mathbf{H}}^{\mathbf{+}}\mathbf{}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}$

${\mathbf{Fe}}^{\mathbf{3}\mathbf{+}}\mathbf{}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{}\mathbf{+}\mathbf{}\mathbf{3}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}\mathbf{}\mathbf{\left(}\mathbf{l}\mathbf{\right)}\mathbf{}\mathbf{\to }\mathbf{}\mathbf{Fe}{\mathbf{\left(}\mathbf{OH}\mathbf{\right)}}_{\mathbf{3}}\mathbf{}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{}\mathbf{+}\mathbf{}\mathbf{3}{\mathbf{H}}^{\mathbf{+}}\mathbf{}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}$

An Iron nail comes into touch with water when it is exposed to a humid environment. As a result of the chemical interaction, it rusts. It becomes damaged as a result of rust and is no longer in use.