Dissolution of a solute is an exothermic process if

Options

A. hydration energy > Lattice energy
B. hydration energy < Lattice energy
C. hydration energy = Lattice energy
D. None of the above

Answer

To determine when the dissolution of a solute is an exothermic process, we need to consider the concepts of hydration energy and lattice energy.

### Step-by-Step Solution:

1. **Understanding Dissolution**:
- Dissolution is the process where a solute dissolves in a solvent to form a solution.

2. **Defining Hydration Energy and Lattice Energy**:
- **Hydration Energy**: This is the energy released when one mole of ions is surrounded by water molecules (hydrated). It is a negative value because energy is released during this process.
- **Lattice Energy**: This is the energy required to break one mole of an ionic compound into its gaseous ions. It is a positive value because energy must be supplied to overcome the forces holding the ions together in the solid lattice.

3. **Energy Changes During Dissolution**:
- When a solute dissolves, energy is required to break the ionic lattice (lattice energy), which is an endothermic process (positive ΔH).
- Simultaneously, energy is released when the solute ions are hydrated (hydration energy), which is an exothermic process (negative ΔH).

4. **Condition for Exothermic Dissolution**:
- For the dissolution process to be exothermic, the energy released during hydration must be greater than the energy required to break the lattice. This can be expressed as:
\[ \text{Hydration Energy} > \text{Lattice Energy} \]
- If this condition is met, the overall change in enthalpy (ΔH) will be negative, indicating that the process is exothermic.

5. **Conclusion**:
- The dissolution of a solute is an exothermic process if the hydration energy is greater than the lattice energy.