The correct answer is acidified copper sulphate.
Key Points
- The process of electrolytic refining is used to purify impure metals.
- In this process, the impure metal is made anode and a thin strip of pure metal is made the cathode.
- A solution of the salt of the metal, which is to be refined is used as an electrolyte.
- In the electrolytic refining of copper acidified copper sulphate is used as an electrolyte.
- On passing the current through the electrolyte, the metal ions from the anode migrate into the solution of the electrolyte and an equivalent amount of metal ion migrates from the solution of electrolyte deposits on the cathode.
- The soluble impuritics go into the solution.
- The insoluble impurities settle down at the bottom as mud which is known as anode mud.
- Reactions at:
- Anode:
Cu(s)⟶Cu2+(aq)+2e− -Cathode:
Cu2+(aq)+2e−⟶Cu(s) - Copper in pure form is transferred from the anode to the cathode.