The carbonate of which of the following cation is soluble in water ?

Options

A. `Na^(+)`
B. `K^(+)`
C. `NH_(4)^(+)`
D. `Ca^(2+)`

Answer

To determine which carbonate is soluble in water among the given cations, we will analyze the solubility of the carbonates formed by each cation.

### Step-by-Step Solution:

1. **Identify the Cations and Their Carbonates**:
- Sodium (Na⁺) forms sodium carbonate (Na₂CO₃).
- Potassium (K⁺) forms potassium carbonate (K₂CO₃).
- Ammonium (NH₄⁺) forms ammonium carbonate ((NH₄)₂CO₃).
- Calcium (Ca²⁺) forms calcium carbonate (CaCO₃).

2. **Check Solubility of Each Carbonate**:
- **Sodium Carbonate (Na₂CO₃)**: Sodium carbonate is soluble in water.
- **Potassium Carbonate (K₂CO₃)**: Potassium carbonate is also soluble in water.
- **Ammonium Carbonate ((NH₄)₂CO₃)**: Ammonium carbonate is soluble in water.
- **Calcium Carbonate (CaCO₃)**: Calcium carbonate is generally insoluble in water.

3. **Conclusion**:
- The carbonates that are soluble in water are:
- Sodium carbonate (Na₂CO₃)
- Potassium carbonate (K₂CO₃)
- Ammonium carbonate ((NH₄)₂CO₃)
- The carbonate that is insoluble in water is calcium carbonate (CaCO₃).

### Final Answer:
The carbonates of sodium, potassium, and ammonium are soluble in water. Therefore, the correct options are A (Sodium), B (Potassium), and C (Ammonium).

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