Question

In electrorefining of metal the impure metal is made anode and a striped pure metal the cathode during the electrolysis of an aqueous solution of a complex metal salt. This method cannot be used for refining of ______.

Options

• silver

• copper

• aluminium

• zinc

Answer 1

In electrorefining of metal the impure metal is made anode and a striped pure metal the cathode during the electrolysis of an aqueous solution of a complex metal salt. This method cannot be used for refining of aluminium.

Explanation:

Highly electropositive metals like aluminium cannot be electro-refined or deposited from an aqueous solution because water has a much higher reduction potential than aluminium ions (Al³⁺). If an aqueous solution is used, hydrogen ions (H⁺) from water will be preferentially reduced at the cathode to produce hydrogen gas instead of depositing the aluminium metal. Therefore, aluminium extraction and subsequent refining must be conducted using a molten electrolyte bath (like in the Hall-Héroult and Hoopes processes) rather than an aqueous solution.