Question

In the silver plating of copper, $K[AG(CN)_2]$ is used instead of $AgNO_3. $ The reason is :-

• A. a thin layer of Ag is formed on Cu
• B. more voltage is required
• C. $Ag^+ $ ions are completely removed from solution
• D. less availability of $Ag^+ $ ions, as Cu cannot displace Ag from $[Ag(CN)_2]^-$ ion

Answer 1

The Correct Option is D

In the silver plating of copper, the use of K[Ag(CN)_2] over AgNO_3 is based on specific chemical properties and reactions involved in the process. Let's analyze the options to understand why K[Ag(CN)_2] is preferred.

1. The use of K[Ag(CN)_2] reduces the availability of Ag^+ ions in the solution. This is because the complex ion [Ag(CN)_2]^− is more stable and Ag+ ions are not freely available for deposition.
2. Copper cannot displace silver from the [Ag(CN)_2]^− ion. Therefore, the deposition of silver onto copper is controlled and more uniform, which enhances the quality of silver plating.
3. This controlled release of silver ions ensures a smooth and adherent coating, reducing the risk of over-accumulation or unbound silver ions in the solution.
4. Additionally, using a complex like K[Ag(CN)_2] prevents the direct exchange reaction where copper would displace silver ions if AgNO_3 were used, as copper is a more reactive metal than silver.

Therefore, the correct answer to the question is: there is less availability of Ag^+ ions, as Cu cannot displace Ag from [Ag(CN)_2]^- ion.