Chemistry - Ionic Equilibrium Question with Solution | TestHub
Which of the following metal halide is least soluble -
Options:
Answer:
Solution:
Lithium fluoride (LiF) is the least soluble among the given alkali metal fluorides. This is due to its high lattice energy, which is a result of the small size of both the Li⁺ and F⁻ ions. The strong electrostatic attraction between these small ions makes it difficult for water molecules to solvate them effectively, leading to lower solubility.
The general trend for alkali metal halides (MX) is that solubility increases down the group for a given halide (e.g., LiF < NaF < KF < RbF < CsF) when lattice energy is the dominant factor. However, for fluorides, the small size of the fluoride ion leads to very high lattice energies, especially with small cations like Li⁺. While hydration energy also plays a role, the exceptionally high lattice energy of LiF makes it less soluble compared to other alkali metal fluorides.
The solubility trend for alkali metal fluorides is: LiF < NaF < KF < RbF < CsF.
Therefore, LiF is the least soluble.