Question

The chemical reactions involved in the rusting of iron are:

• A. Oxidation and displacement
• B. Reduction and combination
• C. Oxidation and combination
• D. Reduction and displacement

Answer 1

The correct option is C

Oxidation and combination

The explanation for the correct option:

(C) Oxidation and Combination reactions

1. Rust is the outcome of a reaction involving iron and oxygen, which is referred to as a combination reaction.
2. Oxidation in the presence of air, moisture, or water causes rusting.

Reactions:

1. Fe is reduced to water at the cathode and oxidized to Fe(II) ions at the anode. The general consensus is positive.

$2\mathrm{Fe}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)+4{\mathrm{H}}^{+}\left(\mathrm{aq}\right)\to 2{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

2. Fe(II) ions are oxidized further to become Fe(III) ions.

$4{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)+4{\mathrm{H}}^{+}\left(\mathrm{aq}\right)\to 4{\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

3. Rust is formed when Fe(III) ions create an insoluble hydrated oxide that is deposited as a red-brown substance.

$2{\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right)+4{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to {\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)+6{\mathrm{H}}^{+}\left(\mathrm{aq}\right)$

The explanation for the incorrect option:

Option (A)

Displacement does not take place in the rusting of iron only oxidation and combination reaction takes place.

Option (B)

The reduction does not take place in the rusting of iron only oxidation and combination reaction takes place.

Option (D)

Rusting of iron does not involve reduction and displacement; instead, it involves oxidation and a combination reaction.

Hence, the correct option is (C).