Potassium cyanide is used for separating

Options

A. `Co^(2+)` and `Ni^(2+)`
B. `Cu^(2+)` and `Cd^(2+)`
C. `Mn^(2+)` and `Zn^(2+)`
D. `Ba^(2+)` and `Ca^(2+)`

Answer

To determine which cations can be separated using potassium cyanide (KCN), we will analyze the reactions of KCN with the given cations.

### Step-by-Step Solution:

1. **Identify the Reaction of KCN with Cations**:
- Potassium cyanide (KCN) is known to form complex ions with certain metal cations. We will look at how it interacts with the cations mentioned in the options.

2. **Reactions with Nickel (Ni)**:
- Nickel reacts with KCN to form potassium nickel cyanide (K2[Ni(CN)4]), also known as potassium niclosinide. This complex is stable and does not release nickel ions in solution.

3. **Reactions with Cobalt (Co)**:
- Cobalt also reacts with KCN to form potassium cobaltosinide (K2[Co(CN)4]). This complex is stable as well and does not release cobalt ions in solution.

4. **Reactions with Cadmium (Cd)**:
- Cadmium reacts with KCN to form K2[Cd(CN)4]. This complex is unstable and will dissociate, releasing cadmium ions (Cd²⁺) into the solution.

5. **Reactions with Copper (Cu)**:
- Copper forms a stable complex with KCN, specifically K3[Cu(CN)4]. This complex does not release copper ions (Cu²⁺) into the solution.

6. **Conclusion**:
- From the analysis, we can conclude that potassium cyanide can be used to separate nickel and cobalt due to the formation of stable complexes that do not release the metal ions. However, it can also separate cadmium due to the instability of its complex, which releases cadmium ions. Copper, on the other hand, forms a stable complex and cannot be separated using KCN.

### Final Answer:
Potassium cyanide is used for separating Nickel (Ni) and Cadmium (Cd) cations.