Which of the following are soluble in water?

Options

A. `Na_(2)CO_(3)`
B. `BaC_(2)O_(4)`
C. `MgCO_(3)`
D. `Ca(NO_(3))_(2)`

Answer

To determine the solubility of the given compounds in water, we will analyze each option based on the solubility rules for salts.

### Step-by-Step Solution:

1. **Option A: Sodium Carbonate (Na2CO3)**
- Sodium carbonate dissociates into sodium ions (Na⁺) and carbonate ions (CO3²⁻).
- According to solubility rules, all sodium salts are soluble in water.
- Therefore, sodium carbonate is soluble in water.

2. **Option B: Barium Oxalate (BaC2O4)**
- Barium oxalate dissociates into barium ions (Ba²⁺) and oxalate ions (C2O4²⁻).
- Oxalates of alkali metals (like sodium and potassium) are soluble, but barium oxalate is part of the alkaline earth metals, which are generally sparingly soluble.
- Therefore, barium oxalate is not soluble in water.

3. **Option C: Magnesium Carbonate (MgCO3)**
- Magnesium carbonate dissociates into magnesium ions (Mg²⁺) and carbonate ions (CO3²⁻).
- Most carbonates are insoluble in water, except for those of sodium, potassium, and ammonium.
- Therefore, magnesium carbonate is not soluble in water.

4. **Option D: Calcium Nitrate (Ca(NO3)2)**
- Calcium nitrate dissociates into calcium ions (Ca²⁺) and nitrate ions (NO3⁻).
- According to solubility rules, all nitrates are soluble in water.
- Therefore, calcium nitrate is soluble in water.

### Summary of Solubility:
- **Sodium Carbonate**: Soluble
- **Barium Oxalate**: Insoluble
- **Magnesium Carbonate**: Insoluble
- **Calcium Nitrate**: Soluble

### Final Answer:
The compounds that are soluble in water are **Sodium Carbonate** and **Calcium Nitrate**.

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