1. Dissolution:
- Copper sulfate, being an ionic compound, dissolves in water. The water molecules surround the copper(II) ions (Cu²⁺) and sulfate ions (SO₄²⁻), breaking apart the ionic bonds holding them together.
2. Hydration:
- The water molecules then form coordinate covalent bonds with the copper(II) ions. This means that the oxygen atom of the water molecule donates a pair of electrons to the copper ion.
- These bonds are stronger than the original ionic bonds in the solid copper sulfate.
3. Formation of Aqua Complex:
- The hydrated copper(II) ions form a complex ion called the hexaaquacopper(II) ion ([Cu(H₂O)₆]²⁺). The copper(II) ion is surrounded by six water molecules.
- The sulfate ions also become hydrated, but their interaction with water is less dramatic.
Overall Reaction:
CuSO₄(s) + 6 H₂O(l) → [Cu(H₂O)₆]²⁺(aq) + SO₄²⁻(aq)
Consequences:
- Color Change: Copper sulfate crystals are white or pale blue. When they dissolve and hydrate, the solution turns a bright blue color. This is due to the absorption of certain wavelengths of light by the hexaaquacopper(II) ion.
- Heat Change: The hydration process is exothermic, meaning it releases heat.
- Conductivity: The solution becomes electrically conductive because of the presence of the free ions.
Important Note:
- Copper sulfate can exist in different hydrated forms. The most common one is copper(II) sulfate pentahydrate (CuSO₄·5H₂O), which contains five water molecules per copper sulfate molecule.
Let me know if you have any further questions!
