Explain:1. Oxidation method (Oxidative refining) 2. Electrolytic refining [5 MARKS]
Explain:1. Oxidation method (Oxidative refining) 2. Electrolytic refining [5 MARKS]
Each point: 2.5 Mark
1. Oxidation method (Oxidative refining) :
This method is used for the refining of metal in those cases in which the impurities have greater tendency to get oxidised than metal itself. For example : Impure iron (Pig or cast iron) is refined by oxidative refining method. Pig iron contains carbon, sulphur, phosphorous, silicon and manganese as impurities. When a blast of air is blown over molten pig iron these impurities are oxidised to their oxides CO2, SO2, P2O5 etc.) and get removed. The pure iron is left behind. Similarly, Silver is refined by this method.
2. Electrolytic refining :
This is the most widely used method for the refining of impure metals. Many metals such as copper, zinc, tin, nickel, silver, gold etc. are refined electrolytically. It is based upon the phenomenon of electrolysis. In this process, the impure metal is made of the anode and a thin strip of pure metal is made of the cathode. A solution of the metal salt is used as an electrolyte. On passing the electric current through the electrolyte, the pure metal from the anode dissolves into electrolyte. An equivalent amount of pure metal gets deposited on the cathode. The soluble impurities go into the solution, where as, the insoluble impurities settle down at the bottom of the anode and are known as anode mud. For example : Electrolytic refining of copper
Each point: 2.5 Mark
1. Oxidation method (Oxidative refining) :
This method is used for the refining of metal in those cases in which the impurities have greater tendency to get oxidised than metal itself. For example : Impure iron (Pig or cast iron) is refined by oxidative refining method. Pig iron contains carbon, sulphur, phosphorous, silicon and manganese as impurities. When a blast of air is blown over molten pig iron these impurities are oxidised to their oxides CO2, SO2, P2O5 etc.) and get removed. The pure iron is left behind. Similarly, Silver is refined by this method.
2. Electrolytic refining :
This is the most widely used method for the refining of impure metals. Many metals such as copper, zinc, tin, nickel, silver, gold etc. are refined electrolytically. It is based upon the phenomenon of electrolysis. In this process, the impure metal is made of the anode and a thin strip of pure metal is made of the cathode. A solution of the metal salt is used as an electrolyte. On passing the electric current through the electrolyte, the pure metal from the anode dissolves into electrolyte. An equivalent amount of pure metal gets deposited on the cathode. The soluble impurities go into the solution, where as, the insoluble impurities settle down at the bottom of the anode and are known as anode mud. For example : Electrolytic refining of copper
