Understanding Electroplating

Electroplating is a process where a thin layer of one metal is deposited onto the surface of another material using an electric current. This process is carried out in an electrolytic cell, which typically contains an electrolyte solution and two electrodes connected to a DC power source.

In the process of electroplating, the material onto which the metal layer is to be deposited serves a specific role within the electrolytic cell. The electric current drives a chemical reaction where metal ions from the electrolyte are attracted to one of the electrodes and gain electrons to become neutral metal atoms, forming a coating on the material.

Connecting the Material to be Electroplated

For successful electroplating, the material that needs to be coated must be placed at the electrode that attracts the positively charged metal ions from the electrolyte. Positively charged ions are called cations. In an electrolytic cell powered by a DC source, cations move towards the negative electrode, which is known as the cathode.

Therefore, the material which is to be electroplated must be connected to the negative terminal of the power supply, making it the cathode. The metal that is being plated (the coating material) often serves as the anode (the positive electrode), or an inert anode is used while the metal ions are sourced from the electrolyte itself.

At the cathode (the material being plated), the metal ions from the solution gain electrons and are deposited as a solid metal layer:

\( \text{M}^{\text{n}+}_{\text{(aq)}} + \text{n e}^{\text{-}} \rightarrow \text{M}_{\text{(s)}} \)

Here, \( \text{M}^{\text{n}+} \) represents the metal ion with a charge of \( \text{n}+ \), and \( \text{M} \) represents the deposited metal.

Analyzing the Options

• Option 1: "can be connected to either cathode or anode". This is incorrect. The material to be plated must be specifically connected as the cathode to attract and deposit positive metal ions.
• Option 2: "is freely kept in the electrolytic tank". This is incorrect. The material must be connected to an electrode (specifically the cathode) to participate in the electrical circuit and receive the metal coating.
• Option 3: "is connected to the terminal of the cathode". This is correct. Connecting the material to the negative terminal makes it the cathode, attracting the metal ions for deposition.
• Option 4: "is connected to the terminal of the anode". This is incorrect. Connecting the material to the positive terminal makes it the anode. The anode would attract negative ions (anions) and repel positive metal ions, preventing deposition.

Based on the principles of electroplating, the material to be coated must be the cathode.