What kind of isomerism exists between `[Cr(H_(2)O)_(6)]Cl_(3)` (violet) and `[Cr(H_(2)O)_(5)Cl].H_(2)O` (greyish-green)?

Options

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

Answer

To determine the type of isomerism that exists between the complexes `[Cr(H₂O)₆]Cl₃` (violet) and `[Cr(H₂O)₅Cl]·H₂O` (greyish-green), we can analyze the nature of these complexes and their structural differences.

### Step-by-Step Solution:

1. **Identify the Coordination Complexes**:
- The first complex is `[Cr(H₂O)₆]Cl₃`, which has six water molecules coordinated to the chromium ion and three chloride ions outside the coordination sphere.
- The second complex is `[Cr(H₂O)₅Cl]·H₂O`, which has five water molecules and one chloride ion coordinated to chromium, with an additional water molecule outside the coordination sphere.

2. **Determine the Molecular Formulas**:
- Both complexes have the same molecular formula: `[Cr(H₂O)₆Cl₃]` and `[Cr(H₂O)₅Cl]·H₂O`.
- The molecular formula can be represented as `CrCl₃·nH₂O`, where `n` varies between the two complexes.

3. **Analyze the Type of Isomerism**:
- **Linkage Isomerism**: This occurs when a ligand can bind to the metal in different ways. This is not applicable here as the ligands (water and chloride) are not changing their mode of attachment.
- **Solvated Isomerism (Hydrate Isomerism)**: This occurs when the number of water molecules coordinated to the metal differs. In this case, one complex has six water molecules while the other has five and one water molecule outside the coordination sphere.
- **Ionization Isomerism**: This occurs when the compounds yield different ions in solution. This is not applicable here as both complexes yield similar ions upon dissociation.
- **Coordination Isomerism**: This occurs in complexes with more than one metal center, which is not the case here.

4. **Conclusion**:
- The isomerism that exists between `[Cr(H₂O)₆]Cl₃` and `[Cr(H₂O)₅Cl]·H₂O` is **solvated isomerism** (or hydrate isomerism) because they differ in the number of water molecules coordinated to the chromium ion.

### Final Answer:
The type of isomerism that exists between `[Cr(H₂O)₆]Cl₃` (violet) and `[Cr(H₂O)₅Cl]·H₂O` (greyish-green) is **solvated isomerism**.