What type of isomerism is shown by the pair `[Cr(H_(2)O)_(6)]Cl_(3)` and `[Cr(H_(2)O)_(5)Cl]Cl_(2).H_(2)O` ?

Options

A. Ionisation isomerism
B. Coordination isomerism
C. Solvate isomerism
D. Linkage isomerism

Explanation

To determine the type of isomerism exhibited by the complexes \([Cr(H_2O)_6]Cl_3\) and \([Cr(H_2O)_5Cl]Cl_2 \cdot H_2O\), we can analyze the structures and the nature of the isomers.

### Step-by-Step Solution:

1. **Identify the Complexes**:
- The first complex is \([Cr(H_2O)_6]Cl_3\), which contains six water molecules coordinated to the chromium ion and three chloride ions outside the coordination sphere.
- The second complex is \([Cr(H_2O)_5Cl]Cl_2 \cdot H_2O\), which has five water molecules and one chloride ion coordinated to chromium, with two chloride ions outside the coordination sphere and one water molecule as a solvate.

2. **Analyze the Coordination Sphere**:
- In the first complex, all six coordination sites are occupied by water molecules, and the three chloride ions are counter ions.
- In the second complex, one of the water molecules is replaced by a chloride ion, resulting in a different arrangement of ligands.

3. **Determine the Type of Isomerism**:
- The key difference between the two complexes is the presence of different ligands in the coordination sphere. The first complex has only water as a ligand, while the second has both water and chloride as ligands.
- This exchange of ligands indicates that these two complexes can be classified as **ionization isomers**. In ionization isomerism, the counter ions (in this case, chloride ions) can be exchanged with the ligands inside the coordination sphere.

4. **Conclusion**:
- Therefore, the type of isomerism shown by the pair \([Cr(H_2O)_6]Cl_3\) and \([Cr(H_2O)_5Cl]Cl_2 \cdot H_2O\) is **ionization isomerism**.