In the silver plating of copper, `K[Ag(CN)_(2)]` is used instead of `AgNO_(3)` . The reason is

Options

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)]^(-)` is

Explanation

To answer the question regarding why potassium silver cyanide, \( K[Ag(CN)_2] \), is used instead of silver nitrate, \( AgNO_3 \), in the silver plating of copper, we can break down the reasoning step by step.

### Step-by-Step Solution:

1. **Understanding Silver Plating**:
- Silver plating involves depositing a layer of silver onto a base metal, in this case, copper (Cu). The process requires a source of silver ions (\( Ag^+ \)).

2. **Comparing Silver Sources**:
- Two potential sources of silver ions are \( K[Ag(CN)_2] \) and \( AgNO_3 \).
- \( K[Ag(CN)_2] \) is a complex compound, while \( AgNO_3 \) is an ionic compound.

3. **Dissociation Characteristics**:
- \( AgNO_3 \) readily dissociates in solution, releasing \( Ag^+ \) ions quickly. This high dissociation rate means that copper can easily displace silver ions from \( AgNO_3 \) due to its higher reactivity.
- In contrast, \( K[Ag(CN)_2] \) is a stable complex. The silver ions are coordinated with cyanide ions, making it difficult for copper to displace the silver ions.

4. **Reactivity of Copper**:
- Copper can displace silver from ionic compounds like \( AgNO_3 \) because it is more reactive than silver. Thus, using \( AgNO_3 \) would result in copper replacing silver ions, which is not desirable for plating.

5. **Stability of the Complex**:
- The stability of \( K[Ag(CN)_2] \) ensures that the silver ions remain available in a form that is less likely to be displaced by copper. This leads to a more controlled and long-lasting plating process.

6. **Conclusion**:
- Therefore, the reason potassium silver cyanide is used instead of silver nitrate in the silver plating of copper is that it provides less availability of \( Ag^+ \) ions, as copper cannot displace silver from the stable complex. This results in a more effective and durable plating process.

### Final Answer:
The correct answer is option 4: "Less availability of \( Ag^+ \) ions as Cu cannot displace Ag from \( K[Ag(CN)_2] \)."