which is not soluble in `CH_(3)COOH` ?

Options

A. `CaC_(2)O_(4)`
B. `Na_(2)C_(2)O_(4)`
C. `K_(2)C_(2)O_(4)`
D. `CaCO_(3)`

Explanation

To determine which compound is not soluble in acetic acid (CH₃COOH), we need to analyze the solubility of the given compounds. In this case, we will focus on calcium oxalate (CaC₂O₄) as the example.

### Step-by-Step Solution:

1. **Identify the Compound**: The compound in question is calcium oxalate (CaC₂O₄).

2. **Understand the Solubility Concept**: Solubility in a solvent depends on the balance between lattice energy (the energy required to separate the ions in a solid) and solvation energy (the energy released when solvent molecules surround and interact with solute ions).

3. **Analyze Calcium Oxalate**:
- **High Lattice Energy**: Calcium oxalate has a high lattice energy, which means a significant amount of energy is required to break the ionic bonds between the calcium ions (Ca²⁺) and oxalate ions (C₂O₄²⁻). This makes it less likely to dissolve in a solvent.
- **Low Solvation Energy**: The solvation energy for calcium oxalate in acetic acid is low, meaning that the energy released when the ions are solvated by acetic acid is not sufficient to overcome the high lattice energy.
- **Comparison with Oxalic Acid**: Oxalic acid (C₂H₂O₄) is more acidic than acetic acid (CH₃COOH). This means that the presence of oxalic acid in the solution can shift the equilibrium and further decrease the solubility of calcium oxalate.

4. **Conclusion**: Based on the above analysis, calcium oxalate (CaC₂O₄) is not soluble in acetic acid (CH₃COOH) due to its high lattice energy, low solvation energy, and the presence of a stronger acid (oxalic acid) in the solution.

### Final Answer:
Calcium oxalate (CaC₂O₄) is not soluble in acetic acid (CH₃COOH).

---