Question

The diagram shows the process of purification of copper metal. A thick copper plate $A$ of impure copper and a thin copper plate $B$ are immersed in a metal sulphate solution and an electric current is passed through it. Which metal solution is taken as electrolyte?

Answer 1

Hint: In the given question, we need to find which metal solution is taken as electrolyte. We will find it with the help of the process of electroplating. Also, here we will explain in detail about the reaction occurring as a result of electroplating.

Complete answer:
In the given diagram we can view that the positive terminal of the battery is connected to the thick rod of impure copper plate and the negative terminal of the battery is connected to the thin rod of pure copper plate because here, the process of electroplating occurs. In the process of electroplating, both an anode and a cathode (the metal part to be coated) are immersed in an electrolytic bath that is composed of a solution of salts, including the metal to be plated.

A direct current is passed through the solution, affecting the transfer of metal ions onto the catholic surface, plating the metal onto the item.According to the concept of electroplating, in the process of purification of copper metal by electrolysis, water soluble salt i.e., copper sulphate solution $\left( {CuS{O_4}} \right)$ is taken as an electrolyte.

Here, when the electric current is passed through electrodes, the copper from thick impure copper plate gets oxidized and dissolved in the solution as $C{u^{ + 2}}$ ions whereas those $C{u^{ + 2}}$ions present in the solution get reduced at the thin pure copper plate. As a result, the thickness of the anode increases and the thickness of the cathode decreases, by which copper is purified.

Note: In this question, it is important to note here that whenever these types of questions are given note the diagram which may help in determining the answer. Here, the chemical effect of electric current is used for electroplating.