Chapter 21, Problem 82A

Interpretation Introduction

Interpretation: An electrolytic cell to show the purification of copper with ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ as the electrolyte needs to be designed. The oxidation and reduction half-reactions need to be given and the overall reaction needs to be balanced.

Concept Introduction: In electrolytic cells, an electric current makes a non-spontaneous redox reaction take place. The process by which electrical energy is converted to chemical energy is known as electrolysis.

Explanation of Solution

Impure metals can be purified in electrolytic cells. In this process, the reduction of cations of molten salts takes place at the cathode to form pure metals.

In the purification of copper, high voltage is applied to dissolve the pure copper metal ions from impure copper metal into the electrolyte (acidified copper sulfate solution in this case). The reaction involved in the formation of copper ions from copper metal takes place at the anode as it is an oxidation reaction. The same amount of copper ions gets deposited at the cathode rod (where the reduction of pure copper ions to pure copper metal takes place).

Thus, the anode is an impure copper rod, the cathode is a pure copper rod, and the electrolyte is acidified copper sulfate solution. The diagram is represented as follows:

  

In this way, impure metal can be refined by the electrolysis method.