Question

How are the less reactive metals (which are quite low in the reactivity series) extracted? Explain with the help of an example.

Answer 1

The ores of less reactive metals, such as copper and mercury, are placed at the bottom of the reactivity series. Metals are extracted from these ores by heating them alone. We should note that copper ores can be extracted by reduction with carbon (copper (I) oxide) as well as by heating alone (copper (I) sulphide).

Let us explain this with the example of extracting mercury from its cinnabar ore (HgS). Cinnabar is a sulphide ore. Heating the ore can extract mercury. It is a sulphide ore; therefore, it is first heated in the presence of surplus air (roasting). This converts mercury (II) sulphide to mercury (II) oxide.

\[\ce{2HgS + 3O2 ->[Roasting][Surplus of air] 2HgO + 2SO2}\]

Mercury (II) oxide is then heated to approximately 300°C. On heating, it gets reduced (decomposes) to mercury metal and oxygen gas is released.

\[\ce{\underset{Mercury (II) oxide}{2HgO} ->[Reduction][Heating 300^\circ C] \underset{Mercury metal}{Hg} + \underset{Oxygen gas}{O2}}\]