Copper sulphate (CuSO₄) solution is acidified with dilute sulphuric acid (H₂SO₄) during electrolysis to ensure efficient and controlled deposition of copper.
Main Reasons:
- Prevents Hydrolysis of Copper Sulphate
Without acid, CuSO₄ can undergo hydrolysis, forming impurities like copper hydroxide. Acidification suppresses this reaction and keeps the solution stable.
- Improves Electrical Conductivity
Sulphuric acid increases the number of ions (H⁺ and SO₄²⁻) in the solution, which enhances conductivity and allows smoother current flow.
- Ensures Pure Copper Deposition
At the cathode, copper ions (Cu²⁺) gain electrons and deposit as pure copper:
Cu²⁺ + 2e⁻ → Cu (solid)
An acidic medium prevents side reactions (like hydrogen gas evolution), ensuring a clean and uniform copper coating.
- Maintains Electrolyte Stability
It keeps the concentration of Cu²⁺ ions consistent, especially when using copper electrodes, helping maintain equilibrium in the system.
Key Takeaway:
Acidifying copper sulphate solution ensures better conductivity, prevents unwanted reactions, and enables pure copper deposition during electrolysis.