1. Copper(II) Ion Hydrolysis:
* When copper sulfate dissolves in water, it dissociates into copper(II) ions (Cu²⁺) and sulfate ions (SO₄²⁻).
* Copper(II) ions are small and highly charged, making them strongly polarizing. This means they attract and pull electron density from the oxygen atoms in water molecules.
* This interaction weakens the O-H bonds in water molecules, making it easier for the hydrogen ions (H⁺) to dissociate.
* The following equilibrium reaction occurs:
```
Cu²⁺(aq) + 2H₂O(l) ⇌ [Cu(H₂O)₄]²⁺(aq) + H⁺(aq)
```
2. Increase in Hydrogen Ion Concentration:
* The hydrolysis reaction produces hydrogen ions (H⁺), which increases the concentration of H⁺ in the solution.
* Since pH is a measure of the hydrogen ion concentration, a higher concentration of H⁺ results in a lower pH value.
3. Acidic Nature:
* A lower pH value indicates acidity. Therefore, the presence of excess hydrogen ions (H⁺) in the solution due to the hydrolysis of the copper(II) ion makes the aqueous solution of copper sulfate acidic.
In summary: The acidity of a copper sulfate solution arises from the hydrolysis of the copper(II) ion, leading to the release of hydrogen ions and a lower pH.
