Name the chemical compound which is electrolyzed in molten state to obtain aluminium metal. Which gas is evolved during this process ?

53 Explain why, an aqueous solution of sodium chloride is not used for the electrolytic extraction of sodium metal. 54 How are metals refined by the electrolytic process? Describe the electrolytic refining of copper with the help of a neat labelled diagram. 55 Name the chemical compound which is electrolyzed in molten state to obtain sodium metal. Which gas is produced in this process ? 55 Name the gas produced when calamine ore is calcined.