Assertion (A): `Na_(2)SO_(4)` is soluble in water while `BaSO_(4)` is insoluble.
Reason (R ): Latice enthalpy of `BaSO_(4)` exceeds its hydration enthalpy.

Options

A. If assertion is true but the reason is false
B. If assertion is false but reason is true
C. If both assertion and reason are true and the reason is the correct explanation of assertion
D. If both assertion and reason are true and the reason is not the correct explanation of assertion

Answer

To solve the question, we will analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
The assertion states that `Na2SO4` is soluble in water while `BaSO4` is insoluble.

- **Explanation**: Sodium sulfate (`Na2SO4`) is soluble in water because sodium ions (Na+) are small and have a high hydration energy. This means that when `Na2SO4` dissolves in water, the energy released from the hydration of sodium ions is sufficient to overcome the lattice energy of the compound, allowing it to dissolve.

- In contrast, barium sulfate (`BaSO4`) is insoluble in water. Barium ions (Ba2+) are larger than sodium ions, which results in lower hydration energy. The lattice energy of `BaSO4` is significantly high, making it difficult for water molecules to break the ionic bonds and dissolve the compound.

### Step 2: Analyze the Reason
The reason states that the lattice enthalpy of `BaSO4` exceeds its hydration enthalpy.

- **Explanation**: Lattice enthalpy is the energy required to separate one mole of an ionic solid into its gaseous ions. For `BaSO4`, the lattice enthalpy is very high due to the large size of both the barium ion and the sulfate ion. This high lattice enthalpy means that a significant amount of energy is required to break the ionic bonds in `BaSO4`.

- Hydration enthalpy is the energy released when ions are surrounded by water molecules. For `BaSO4`, the hydration enthalpy is not sufficient to overcome the high lattice enthalpy, which is why `BaSO4` remains insoluble in water.

### Step 3: Conclusion
Both the assertion and the reason are true. The reason correctly explains why the assertion is true.

### Final Answer
- **Assertion (A)**: True
- **Reason (R)**: True
- **Explanation**: The reason provided correctly explains the solubility behavior of `Na2SO4` and `BaSO4` in water.

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