Read the passage given below and answer the following questions :
The existence of coordination compounds with the same formula but different arragements of the ligands was crucial in the development of coordination chemistry. Two or more compounds with the same formula but different arrangements of the atoms are called isomers. Isomers are compounds with the same molecular formula but different structural formulas and do not necessarily share similar properties. There are many different classes of isomers, like stereoisomers, enantiomers, and geometrical isomers. There are two main forms of isomerism: structural isomerism and stereoisomerism. The different chemical formulas in structural isomers are caused either by a difference in what ligands are bonded to the central atoms or how the individual ligands are bonded to the central atoms.
The following questions are multiple choice questions. Choose the most appropriate answer:
What kind of isomerism exists between `[Cr(H_(2)O)_(6)] Cl_(3)` (violet) and `[Cr(H_(2)O)_(5)Cl]Cl_(2).H_(2)O` (greyishgreen) ?

Options

A. linkage isomerism
B. solvate isomerism
C. ionization isomerism
D. coordinate isomerism

Answer

To solve the question regarding the type of isomerism that exists between the two coordination compounds `[Cr(H₂O)₆]Cl₃` (violet) and `[Cr(H₂O)₅Cl]Cl₂·H₂O` (greyish green), we can follow these steps:

### Step 1: Identify the Coordination Compounds
We have two coordination compounds:
1. `[Cr(H₂O)₆]Cl₃`
2. `[Cr(H₂O)₅Cl]Cl₂·H₂O`

### Step 2: Analyze the Ligands and Their Arrangements
- In the first compound, there are six water molecules coordinated to the chromium ion and three chloride ions outside the coordination sphere.
- In the second compound, there are five water molecules and one chloride ion coordinated to the chromium ion, with two chloride ions outside the coordination sphere and one water molecule as a hydrate.

### Step 3: Determine the Type of Isomerism
The key difference between the two complexes lies in the arrangement of the ligands:
- The first compound has all six ligands as water.
- The second compound has one of the water ligands replaced by a chloride ion.

This indicates that the isomerism is due to the different arrangements of ligands around the central metal ion, which can be classified as **coordination isomerism**.

### Step 4: Conclusion
Based on the analysis, the type of isomerism that exists between `[Cr(H₂O)₆]Cl₃` and `[Cr(H₂O)₅Cl]Cl₂·H₂O` is **coordination isomerism**.

### Final Answer
The correct answer is **coordination isomerism**.

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