In the electrolytic refining of a metal M, the anode, cathode, and electrolyte would be selected as follows:
Anode: The anode is typically made of impure metal M that needs to be refined. During electrolysis, the metal atoms at the anode lose electrons and dissolve into the electrolyte as positively charged ions (cations). For example, if refining copper (Cu), the anode would be made of impure copper.
Cathode: The cathode is usually made of a pure metal or a highly pure form of metal M. Metal ions from the electrolyte are attracted to the cathode, where they gain electrons and deposit onto the cathode as pure metal atoms. For example, if refining copper, the cathode would be made of pure copper.
Electrolyte: The electrolyte is a solution containing ions of the metal to be refined. It allows the flow of electric current between the anode and cathode. The choice of electrolyte depends on the metal being refined. It should contain ions of the metal in its cationic form. For example, in the electrolytic refining of copper, the electrolyte is typically a solution of copper sulfate (CuSO4) or copper chloride (CuCl2).
So, in summary:
- Anode: Impure metal M
- Cathode: Pure metal M
- Electrolyte: Solution containing ions of metal M in its cationic form