`MgCO_(3)` is not precipitated with the carbonates of Vth group radicals in presence of `NH_(4)Cl and NH_(4)OH` because:

Options

A. `MgCO_(3)` is soluble in `NH_(4)OH`
B. `MgCO_(3)` is not precipitated in presence of `NH_(4)Cl`
C. `MgCO_(3)` is soluble in water
D. `MgCO_(3)` is soluble in `(NH_(4))_(2)CO_(3)`

Answer

To understand why MgCO₃ is not precipitated with the carbonates of the Vth group radicals in the presence of NH₄Cl and NH₄OH, we can break down the explanation into a series of logical steps:

### Step-by-Step Solution:

1. **Identify the Groups**:
- Magnesium (Mg) belongs to the 4th group of cations, while calcium (Ca) and other elements belong to the 5th group of cations.

2. **Understanding the Role of Ammonium Compounds**:
- When NH₄Cl (ammonium chloride) and NH₄OH (ammonium hydroxide) are added, they introduce ammonium ions (NH₄⁺) into the solution.

3. **Common Ion Effect**:
- The presence of NH₄⁺ ions leads to the common ion effect, which influences the solubility of salts in solution. The common ion effect states that the solubility of a salt decreases when a common ion is added to the solution.

4. **Formation of Carbonate Ions**:
- In the presence of NH₄₂CO₃ (ammonium carbonate), both MgCO₃ and CaCO₃ can theoretically form. However, the added NH₄⁺ ions affect the concentration of carbonate ions (CO₃²⁻) in the solution.

5. **Decrease in Carbonate Ion Concentration**:
- The addition of NH₄⁺ ions decreases the concentration of carbonate ions due to the common ion effect. As the concentration of CO₃²⁻ decreases, the solubility product (Ksp) of the carbonates comes into play.

6. **Comparison of Ksp Values**:
- The Ksp of MgCO₃ is lower than that of the carbonates of the 5th group (like CaCO₃). Therefore, as the concentration of CO₃²⁻ decreases, the Ksp of the carbonates of the 5th group is exceeded, leading to their precipitation.

7. **Solubility of MgCO₃**:
- Since the Ksp for MgCO₃ does not exceed the lowered concentration of carbonate ions, MgCO₃ remains soluble in the presence of NH₄Cl and NH₄OH.

8. **Conclusion**:
- Therefore, MgCO₃ is not precipitated because it remains soluble due to the common ion effect and the relative Ksp values of the carbonates involved.

### Final Answer:
MgCO₃ is not precipitated with the carbonates of the Vth group radicals in the presence of NH₄Cl and NH₄OH because it remains soluble due to the common ion effect, which decreases the concentration of carbonate ions, preventing the precipitation of MgCO₃.

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