Question

Explain how the following metals are obtained from their compounds by the reduction process.

(a) Metal X which is low in reactivity series

(b) Metal Y which is in the middle of the reactivity series

(c) Metal Z which is high up in the reactivity series.

Answer 1

(a)

• Metal oxides of the less reactive metals like Mercury ($\mathbf{Hg}$), Copper ($\mathbf{Cu}$) is reduced by heat reduction method.
• In this method, Sulphide ores of Mercury, Copper, etc are heated in presence of air. A part of the ore gets oxidised to Oxide
• And the remaining Sulphide ore undergoes reaction with metal oxide to produce metal and Sulphur dioxide gas.

$$\begin{gathered} 2\mathrm{HgS}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2\mathrm{HgO}\left(\mathrm{s}\right)+2{\mathrm{SO}}_2\left(\mathrm{g}\right) \\ \mathrm{Cinnabar}\mathrm{Oxygen}\mathrm{Mercuric}\mathrm{Sulphur} \\ \mathrm{oxide}\mathrm{dioxide} \end{gathered}$$

(b)

• Oxides of the metals that are moderately reactive like Iron, Zinc, etc. are reduced by the Carbon reduction method.
• In this method, metal oxide is reduced by Carbon to produce metal and Carbon monoxide gas.
• For example,

$$\begin{gathered} {\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+3\mathrm{C}\left(\mathrm{g}\right)\to 2\mathrm{Fe}\left(\mathrm{s}\right)+3\mathrm{CO}\left(\mathrm{g}\right) \\ \mathrm{Ferric}\mathrm{Carbon}\mathrm{Iron}\mathrm{Carbon} \\ \mathrm{oxide}\mathrm{monoxide} \end{gathered}$$

(c)

• The oxides of metals of high reactivity such as Sodium ($\mathbf{Na}$), Potassium ($\mathbf{K}$) cannot be reduced by Carbon or Aluminium.
• This is because of the high stability of the cation (highly electropositive).
• These metal oxides are reduced by the electrolytic reduction method.
• In this method, the reduction of the cation of the metal is done by passing electricity through its molten Chloride or oxide.
• For example, extraction of Sodium is done by this method.