Chapter 20.3, Problem 26SSC

Interpretation Introduction

Interpretation:

Cathode and anode of that electrolytic cell in which gold plating of an object is done is to be described.

Concept introduction:

Electroplating is method utilized to refine various metals like $\text{Cu}$. In this process, a metal coating is developed on a solid metal surface through reduction of its cations by flow of current by means of external voltage application. It improves thickness, wear resistance and protects metal from corrosion.

Answer to Problem 26SSC

In gold electroplating, the object to be coated with gold act as cathode and gold sheet or bar acts as anode.

Explanation of Solution

In gold electroplating, the object to be coated with gold act as cathode and gold sheet or bar acts as anode with $\text{AuCN}$ in water as electrolytic solution. When direct current flows, oxidation of $\text{Au}$ from $\text{AuCN}$ to ${\text{Au}}^{+}$ ions occurs at anode. ${\text{Au}}^{+}$ ions are neutralized by electrons at anode. Since electrons are lost at anode bar to form ${\text{Au}}^{+}$ ions, it gradually gets dissolved into solution to restore ${\text{Au}}^{+}$ ions in it. As a result $\text{Au}$ metal gets transferred from anode to cathode and this process continues until desired thickness of coating on cathode is achieved. This results into a development of coating of gold onto the object.

Conclusion

In gold electroplating, the object to be coated with gold act as cathode and gold sheet or bar acts as anode.