Question

Explain oxidation-reduction reactions in terms of gain or loss of oxygen or hydrogen by giving one suitable example of each

Answer 1

1. Oxidation: Oxidation is defined as the gain of an oxygen ($\mathrm{O}$) atom or the removal of a hydrogen ($\mathrm{H}$) atom.
2. Examples:

(i) Oxidation as the addition of oxygen: oxidation of carbon: $$\begin{gathered} \mathrm{C}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{CO}}_2\left(\mathrm{g}\right) \\ \mathrm{Carbon}\mathrm{Oxygen}\mathrm{Carbon}\mathrm{dioxide} \end{gathered}$$

(ii) Oxidation as removal of hydrogen: oxidation of Sulphur: $$\begin{gathered} \underset{}{{\mathrm{H}}_2\mathrm{S}}\left(\mathrm{aq}\right)+{\mathrm{Br}}_2\left(\mathrm{g}\right)\to 2\mathrm{HBr}\left(\mathrm{aq}\right)+\mathrm{S}\left(\mathrm{s}\right) \\ \mathrm{Hydrogen}\mathrm{Bromine}\mathrm{Hydrogen}\mathrm{Sulphur} \\ \mathrm{sulphide}\mathrm{bromide} \end{gathered}$$

3. Reduction: Reduction is defined as the gain of a hydrogen ($\mathrm{H}$) atom or the removal of an oxygen ($\mathrm{O}$) atom.

4. Examples:

(i) Reduction as the addition of hydrogen: reduction of nitrogen: $$\begin{gathered} {\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\to 2{\mathrm{NH}}_3\left(\mathrm{g}\right) \\ \mathrm{Nitrogen}\mathrm{Hydrogen}\mathrm{Ammonia} \end{gathered}$$

(ii) Reduction as the removal of oxygen: reduction of zinc oxide: $$\begin{gathered} \mathrm{ZnO}\left(\mathrm{s}\right)+\mathrm{C}\left(\mathrm{s}\right)\to \mathrm{Zn}\left(\mathrm{s}\right)+\mathrm{CO}\left(\mathrm{g}\right) \\ \mathrm{Zinc}\mathrm{Carbon}\mathrm{Zinc}\mathrm{Carbon}\mathrm{monoxide} \\ \mathrm{oxide} \end{gathered}$$