In `CuSO_(4) · 5H_(2)O`

Options

A. all the five water molecules act as ligands
B. all the five `H_(2)O` molecules are attached to `Cu^(2 +)` ion
C. four `H_(2)O` molecules are coordinated to central `Cu^(2+)` ion while the fifth `H_(2)O` molecule is attached to `SO_(4)^(2-)` by hydrogen bonds
D. all the five water molecules occupy interstitial sites in the crystal lattice.

Answer

To solve the question regarding the structure of `CuSO₄ · 5H₂O`, we will analyze the coordination of water molecules in the compound step by step.

### Step-by-Step Solution:

1. **Identify the Components**:
- The compound `CuSO₄ · 5H₂O` consists of copper sulfate and five water molecules.
- `Cu` refers to copper, `SO₄` refers to the sulfate ion, and `H₂O` refers to water.

2. **Understand the Coordination Chemistry**:
- In coordination chemistry, ligands are molecules or ions that can donate a pair of electrons to a metal ion to form a coordinate bond.
- Water (H₂O) can act as a ligand because it has lone pairs of electrons on the oxygen atom.

3. **Determine the Oxidation State of Copper**:
- In `CuSO₄`, copper is in the +2 oxidation state (Cu²⁺).

4. **Analyze the Water Molecules**:
- In the hydrated form `CuSO₄ · 5H₂O`, the five water molecules are associated with the copper ion and the sulfate ion.
- Typically, in such complexes, some water molecules coordinate directly to the metal ion while others may interact with other ions through hydrogen bonding.

5. **Identify the Coordination**:
- It is known that in `CuSO₄ · 5H₂O`, four water molecules coordinate to the Cu²⁺ ion.
- The fifth water molecule does not coordinate directly to the copper ion but instead forms hydrogen bonds with the sulfate ion.

6. **Conclusion**:
- Therefore, the correct statement regarding the arrangement of water molecules in `CuSO₄ · 5H₂O` is that four water molecules are coordinated to the central copper ion, while the fifth water molecule is attached to the sulfate ion by hydrogen bonds.

### Final Answer:
The correct option is **C**: Four water molecules are coordinated to the central copper (II) ion while the fifth is attached to the sulfate ion by hydrogen bonds.

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