Question

State giving reason the reduction process to obtain the following metals from their compounds:
(i) Mercury,
(ii) Copper and
(iii) Sodium

Answer 1

Mercury: Mercury is typically obtained from its ore cinnabar (HgS) by the process of heating in the presence of oxygen, followed by reduction with heat alone. The reaction is:
\[\text{HgS} + \text{O}_2 \rightarrow \text{Hg} + \text{SO}_2\]
This process is feasible because mercury is a metal that can be vaporized at a relatively low temperature.
Copper: Copper is extracted from copper(I) sulfide after concentrating the ore by froth flotation. The ore is then heated in air to convert it to copper(II) oxide, which is reduced to copper using carbon as a reducing agent:
\[2\text{Cu}_2\text{O} + \text{C} \rightarrow 4\text{Cu} + \text{CO}_2\]
Carbon is used because it can economically reduce copper oxide to copper metal at high temperatures.
Sodium: Sodium is obtained from electrolysis of molten sodium chloride (NaCl), not by reduction of its compounds with carbon. This is because sodium has a strong affinity for oxygen and forms stable compounds that are difficult to reduce with traditional carbon reduction:
\[2\text{NaCl} \rightarrow 2\text{Na} + \text{Cl}_2 \quad (\text{using electrolysis})\]
Electrolysis is used due to the reactivity of sodium and its ability to reduce sodium chloride directly to metal and chlorine gas.