The lattice energy of Lithium Chloride (LiCl) is 829 kJ/mol. This value represents the energy released when gaseous ions combine to form one mole of a solid ionic compound, or conversely, the energy required to break one mole of the solid into its constituent gaseous ions.
Understanding Lattice Energy
Lattice energy is a crucial concept in understanding the stability and properties of ionic compounds. It is a measure of the strength of the electrostatic forces holding the ions together in the crystal lattice. A higher lattice energy generally indicates a more stable ionic compound.
Lattice Energy of Common Ionic Compounds
The lattice energy is typically expressed in kilojoules per mole (kJ/mol) and is an important thermodynamic quantity. For LiCl, the specific value is given in the table below, alongside other related compounds for comparison:
| Compound | Lattice Energy (kJ/mol) |
|---|---|
| LiCl | 829 |
| LiBr | 789 |
| LiI | 734 |
| CuCl | 979 |
As seen from the table, LiCl has a high lattice energy, indicating strong ionic bonds within its crystal structure. The lattice energy tends to decrease as the size of the halide ion increases (from Cl⁻ to Br⁻ to I⁻), due to the greater internuclear distance and weaker electrostatic attraction.
Factors Influencing Lattice Energy
Several factors influence the magnitude of lattice energy:
- Ionic Charge: Compounds formed from ions with higher charges (e.g., Mg²⁺O²⁻ vs. Na⁺Cl⁻) typically have significantly higher lattice energies because the electrostatic attraction is directly proportional to the product of the ionic charges.
- Ionic Radius: Smaller ionic radii lead to stronger electrostatic attractions between the ions and thus higher lattice energies. This is because the distance between the centers of the ions is smaller, resulting in a stronger force of attraction. For instance, comparing LiCl, LiBr, and LiI, the lattice energy decreases as the halide ion gets larger (Cl < Br < I).
Understanding the lattice energy of LiCl helps in predicting its physical properties, such as its high melting point and its tendency to be soluble in polar solvents.
