The following questions refer to the extraction of alumnium and iron f

1.	The following questions refer to the extraction of alumnium and iron from their ores : (i) “Name the principal ore from which; (a) iron and (b) aluminium are extracted. (ii) What is the most important chemical process in the extraction of any metal ? State how this essential step is carried out in the extraction of; (a) iron, (b) aluminium. (iii) Iron and aluminium ores both, contain impurities. Explain briefly how these impurities are removed in each case. (iv) What is the major impurity present in iron when it is removed from the blast furnace ?
Answer» (i) (a) Haematite (Fe₂O₃ ). (b) Bauxite (Al₂O₃ ). (ii) Reduction of the oxide is an important step in extraction of metal. In case of iron, Fe₂O₃ + 3CO ⟶ 2Fe + 3CO₂ Al₂O₃ cannot be easily reduced, hence it is subjected to electrolysis. Aluminium is collected at the cathode. (iii) Iron ore contains impurities of silica and sand. These are removed by magnetic separation. Bauxite and aluminium ore contains impurities of FeO and SiO₂ . Bauxite containing FeO is calcinated at high temperature when FeO is oxidised to Fe₂O₃ . Calcinated ore is then treated with NaOH when Al₂O₃ is converted into soluble NaAlO₂ .Fe₂O₃ can thus be filtered off. Bauxite containing SiO₂ is mixed with coke and heated to 1000°C in an atmosphere of N₂ . Silica is reduced to Si which volatilises at the temperature of reaction. Aluminium oxide is converted into AIN which is hydrolysed with water to obtain Al(OH)₃ . (iv) Carbon is major impurity present in iron.

The following questions refer to the extraction of alumnium and iron from their ores : (i) “Name the principal ore from which; (a) iron and (b) aluminium are extracted. (ii) What is the most important chemical process in the extraction of any metal ? State how this essential step is carried out in the extraction of; (a) iron, (b) aluminium. (iii) Iron and aluminium ores both, contain impurities. Explain briefly how these impurities are removed in each case. (iv) What is the major impurity present in iron when it is removed from the blast furnace ?

Answer»

(i) (a) Haematite (Fe₂O₃ ).

(b) Bauxite (Al₂O₃ ).

(ii) Reduction of the oxide is an important step in extraction of metal. In case of iron, Fe₂O₃ + 3CO ⟶ 2Fe + 3CO₂ Al₂O₃ cannot be easily reduced, hence it is subjected to electrolysis. Aluminium is collected at the cathode.

(iii) Iron ore contains impurities of silica and sand. These are removed by magnetic separation. Bauxite and aluminium ore contains impurities of FeO and SiO₂ . Bauxite containing FeO is calcinated at high temperature when FeO is oxidised to Fe₂O₃ . Calcinated ore is then treated with NaOH when Al₂O₃ is converted into soluble NaAlO₂ .Fe₂O₃ can thus be filtered off. Bauxite containing SiO₂ is mixed with coke and heated to 1000°C in an atmosphere of N₂ . Silica is reduced to Si which volatilises at the temperature of reaction. Aluminium oxide is converted into AIN which is hydrolysed with water to obtain Al(OH)₃ .

(iv) Carbon is major impurity present in iron.

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