BeO is insoluble but BaO is soluble as

Options

A. lattice energy of `BeO` is higher than BaO due to small size of `Be^(2+)` ion and its covalent nature
B. hydration energy of BeO is lower than BaO due to small size `Be^(2+)` ion
C. BeO is amphoteric in nature while BaO is basic
D. BeO forms hydrated salts while BaO forms anhydrous salts

Explanation

To understand why BeO is insoluble while BaO is soluble, we need to analyze the concepts of lattice enthalpy and hydration enthalpy.

### Step-by-Step Solution:

1. **Understanding Lattice Enthalpy**:
- Lattice enthalpy is the energy required to separate one mole of an ionic solid into its gaseous ions. It is always a positive value because energy must be supplied to overcome the electrostatic forces holding the ions together.
- The lattice enthalpy depends on two factors: the charge of the ions and their ionic radii. Higher charges and smaller ionic radii result in higher lattice enthalpy.

2. **Understanding Hydration Enthalpy**:
- Hydration enthalpy is the energy released when gaseous ions are surrounded by water molecules and solvated. This value is always negative because energy is released during the solvation process.
- Similar to lattice enthalpy, hydration enthalpy also depends on the charge density of the ions. Higher charge density leads to greater hydration enthalpy.

3. **Analyzing BeO**:
- Beryllium oxide (BeO) consists of Be²⁺ and O²⁻ ions. The Be²⁺ ion has a small ionic radius and a high charge, resulting in a very high lattice enthalpy.
- The hydration enthalpy of Be²⁺ is not sufficient to overcome the high lattice enthalpy of BeO. Therefore, BeO remains insoluble in water.

4. **Analyzing BaO**:
- Barium oxide (BaO) consists of Ba²⁺ and O²⁻ ions. The Ba²⁺ ion has a larger ionic radius compared to Be²⁺, which results in a lower lattice enthalpy for BaO.
- The hydration enthalpy of Ba²⁺ is sufficiently high to overcome the lattice enthalpy of BaO, allowing it to dissolve in water.

5. **Conclusion**:
- BeO is insoluble because its lattice enthalpy is greater than its hydration enthalpy, while BaO is soluble because its hydration enthalpy is greater than its lattice enthalpy.

### Final Answer:
BeO is insoluble due to its high lattice enthalpy, which exceeds its hydration enthalpy, while BaO is soluble because its hydration enthalpy surpasses its lattice enthalpy.

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