Which of the following is least soluble in water ?

Options

A. AgCl
B. AgBr
C. AgI
D. AgF

Answer

To determine which of the following silver halides is least soluble in water, we will analyze the solubility of AgCl, AgBr, AgI, and AgF based on their lattice energies and hydration energies.

### Step-by-Step Solution:

1. **Identify the Silver Halides**: The compounds we are considering are:
- AgCl (Silver Chloride)
- AgBr (Silver Bromide)
- AgI (Silver Iodide)
- AgF (Silver Fluoride)

2. **Understand Lattice Energy and Hydration Energy**:
- **Lattice Energy**: This is the energy required to separate one mole of a solid ionic compound into its gaseous ions. Higher lattice energy means the compound is less soluble in water.
- **Hydration Energy**: This is the energy released when ions are surrounded by water molecules. Higher hydration energy can increase solubility.

3. **Analyze the Trend in Solubility**:
- The solubility of silver halides in water generally decreases as the size of the halide ion increases. This is because larger ions (like I⁻) have lower hydration energy compared to smaller ions (like F⁻).
- The order of solubility for silver halides in water is as follows:
- AgF > AgCl > AgBr > AgI

4. **Conclusion**:
- From the order of solubility, we can conclude that **AgI (Silver Iodide)** is the least soluble in water.

5. **Final Answer**:
- Therefore, the answer to the question is **AgI**.