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 (sodium, potassium, ammonium, and calcium), we can follow these steps:

### Step 1: Identify the cations
The cations we are considering are:
- Sodium (Na⁺)
- Potassium (K⁺)
- Ammonium (NH₄⁺)
- Calcium (Ca²⁺)

### Step 2: Recall the solubility rules for carbonates
Generally, carbonates (CO₃²⁻) are mostly insoluble in water, with some exceptions. The carbonates of alkali metals (Group 1 elements) and ammonium are soluble in water.

### Step 3: Analyze each cation
1. **Sodium (Na⁺)**: Sodium carbonate (Na₂CO₃) is soluble in water.
2. **Potassium (K⁺)**: Potassium carbonate (K₂CO₃) is also soluble in water.
3. **Ammonium (NH₄⁺)**: Ammonium carbonate ((NH₄)₂CO₃) is soluble in water.
4. **Calcium (Ca²⁺)**: Calcium carbonate (CaCO₃) is generally insoluble in water.

### Step 4: Conclusion
Based on the analysis, the carbonates of sodium, potassium, and ammonium are soluble in water, while calcium carbonate is not.

### Final Answer
The carbonates of the following cations are soluble in water: Sodium (Na⁺), Potassium (K⁺), and Ammonium (NH₄⁺).