What is hydrolysis? How does adding sulphuric acid to aqueous copper sulphate prevent it?

Hydrolysis is a chemical reaction in which a compound reacts with water, resulting in the breakdown of the compound and formation of new substances. In aqueous solutions, hydrolysis often involves salts reacting with water to produce acidic or basic solutions.

In the case of copper sulphate (CuSO₄) dissolved in water, a slight hydrolysis can occur:

Cu²⁺ + H₂O ⇌ CuOH⁺ + H⁺

This reaction releases H⁺ ions, making the solution slightly acidic and leading to the formation of basic salts like Cu(OH)₂ under certain conditions.

How does adding sulphuric acid prevent hydrolysis?

When dilute sulphuric acid (H₂SO₄) is added to the copper sulphate solution:

• It increases the concentration of H⁺ ions in the solution.
• According to Le Chatelier’s Principle, the equilibrium shifts backward to reduce excess H⁺ ions.
• This suppresses hydrolysis and keeps copper ions stable in solution.

Key Takeaway:

Adding sulphuric acid prevents hydrolysis by maintaining a high acidic environment, which stabilizes Cu²⁺ ions and stops the formation of unwanted hydroxide compounds.