Question

In the silver plating of copper, \( K[\text{Ag(CN)}_2] \) is used instead of \( \text{AgNO}_3 \). The reason is:

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

Hint:

Using complex ions in electroplating allows for better control of metal ion concentration and plating quality.

Answer 1

The Correct Option is D

Step 1: The complex \( K[\text{Ag(CN)}_2] \) is used in silver plating because \( \text{Ag}^+ \) is more stable in the complex ion than as a free ion.
Step 2: The use of \( [\text{Ag(CN)}_2]^- \) ensures that \( \text{Ag}^+ \) ions are available in a controlled form, and copper cannot displace \( \text{Ag}^+ \) from this complex.

Final Answer: \[ \boxed{\text{less availability of } \text{Ag}^+ \text{ ions, as Cu cannot displace Ag from } [\text{Ag(CN)}_2]^- \text{ ion}} \]