Chapter 20.3, Problem 24SSC

Interpretation Introduction

Interpretation:

Process of purification of impure copper by smelting of ore by electrolysis is to be explained.

Concept introduction:

Electrochemistry is study of relation between electrical energy and chemical changes that takes place in redox reaction. There are three main aspects of electrochemistry branch, those are:

1. Electrolysis
2. Electrochemical cell
3. Electrolytic conduction.

Electrolysis is a process in which decomposition of electrolyte occurs on flow of electricity through its aqueous solution or molten state. The instrument employed to carry out electrolysis is electrolytic cell. Example of electrolytic cell is when a secondary battery is recharged.

Answer to Problem 24SSC

In smelting process, molten $\text{Cu}$ is casted into thick plates which act as anode in electrolytic cell. The electrolyte used is ${\text{CuSO}}_4$ with a thin $\text{Cu}$ sheet as cathode. On flow of current, $\text{Cu}$ from impure anode oxidizes to ${\text{Cu}}^{2+}$ ions. These ions migrate to cathode for reduction into $\text{Cu}$ atoms and impurities leave behind at the bottom of solution or electrolyte.

Explanation of Solution

One of the applications of Electrolysis is also found in purification of metals like $\text{Cu}$. $\text{Cu}$ is mainly mined in form of its sulfide ores as they are most abundant. Examples of copper ores are chalcopyrite $\left({\text{CuFeS}}_{\text{2}}\right)$ and malachite $\left({\text{Cu}}_{\text{2}}{\text{CO}}_{\text{3}}{\left(\text{OH}\right)}_{\text{2}}\right)$.

On heating sulfide ore in presence of oxygen, copper is obtained as follows:

${\text{Cu}}_{\text{2}}\text{S}\left(\text{s}\right)+{\text{O}}_{\text{2}}\left(\text{g}\right)\to \text{2Cu}\left(\text{l}\right)+{\text{SO}}_{\text{2}}\left(\text{g}\right)$

$\text{Cu}$ obtained by this smelting process is refined for purification from impurities. For purification, molten $\text{Cu}$ is casted into thick plates which act as anode in electrolytic cell. The electrolyte used is ${\text{CuSO}}_4$ with a thin $\text{Cu}$ sheet as cathode. On flow of current, $\text{Cu}$ from impure anode oxidizes to ${\text{Cu}}^{2+}$ ions. These ions migrate to cathode for reduction into $\text{Cu}$ atoms and impurities leave behind at the bottom of solution or electrolyte.

Conclusion

In smelting process, molten $\text{Cu}$ is casted into thick plates which act as anode in electrolytic cell. The electrolyte used is ${\text{CuSO}}_4$ with a thin $\text{Cu}$ sheet as cathode. On flow of current, $\text{Cu}$ from impure anode oxidizes to ${\text{Cu}}^{2+}$ ions. These ions migrate to cathode for reduction into $\text{Cu}$ atoms and impurities leave behind at the bottom of solution or electrolyte.