Question

The diagram given below shows the electroplating of a spoon with silver. With reference to the diagram, answer the following questions. 
(a) Write an equation for the reaction that occurs at the cathode. 
(b) Silver nitrate solution is not preferred as an electrolyte in the above process. Give a reason. 
(c) Why is alternating current not used in the process? 
(d) What is the observation at the anode? 

 

Hint:

To ensure a perfect finish during electroplating, the article to be plated must always be placed at the Cathode and the electrolyte must contain ions of the metal to be deposited!

Answer 1

(a) Equation for the reaction at the cathode:
The spoon is the cathode, so reduction takes place at the cathode.
Silver ions from the electrolyte gain electrons and get deposited on the spoon as silver metal.

Cathode reaction:
Ag⁺ + e^- → Ag

(b) Why is silver nitrate solution not preferred as the electrolyte?
Silver nitrate solution is not preferred because it releases silver ions in high concentration.
Due to this, silver gets deposited very rapidly and the coating formed becomes rough, uneven and non-uniform.
In electroplating, a smooth and firm coating is needed, so a complex salt like sodium argentocyanide solution is used instead because it provides silver ions slowly and steadily.

(c) Why is alternating current not used in the process?
Alternating current is not used because the direction of current keeps changing continuously.
As a result, the cathode and anode would keep exchanging their functions.
This would prevent proper deposition of silver on the spoon and electroplating would not occur effectively.
Therefore, direct current (DC) is used.

(d) Observation at the anode:
The silver anode gradually dissolves into the electrolyte.
Its size decreases because silver atoms lose electrons and enter the solution as silver ions.

Anode reaction:
Ag → Ag⁺ + e^-

Final Answers:
(a) Ag⁺ + e^- → Ag
(b) Silver nitrate is not preferred because it causes fast, rough and uneven deposition of silver.
(c) Alternating current is not used because the electrodes would keep changing their roles, so proper electroplating cannot take place.
(d) The silver anode gradually dissolves and becomes thinner.